Prerequisites
This lesson is part of the RYA/MCA Yachtmaster Offshore syllabus. You should already:
- Be able to keep a basic navigational log, work up an EP and plot fixes (Day Skipper and Coastal Skipper navigation).
- Understand watch systems and fatigue management (covered earlier in this course).
- Know the Beaufort scale, how to read a barometer and how to describe sea state and visibility.
- Be building your own sea time record. Yachtmaster Offshore candidates need 50 days at sea, 2,500 miles, at least 5 days as skipper and 5 passages over 60 miles (2 overnight, 2 as skipper). The examiner will check your personal log, signed by the skippers concerned, as evidence of this.
Learning Objectives
By the end of this lesson you should be able to:
- Explain why logs matter: safety, navigation, legal evidence and insurance.
- Distinguish between the navigational (deck) log, official records and maintenance records, and state what goes in each.
- Keep a navigation log to an appropriate standard: content, frequency and style.
- Write factual, objective entries and correct mistakes properly.
- Record watches and rest hours, drills, incidents and equipment defects.
- Structure an incident report.
- Present your personal sea time record for the Yachtmaster Offshore exam.
- Identify the ship's papers, licences and certificates a skipper must carry, and the reporting duties after a collision or accident.
RYA syllabus mapping. This lesson covers the Yachtmaster Offshore course objectives for log keeping and documentation: maintain an official log with all mandatory entries in a legally defensible format; keep the navigation log with appropriate position-fixing intervals and weather observations; track maintenance, safety equipment inspections and defect reports; and understand the legal status of logbooks as evidence in investigations. It also supports the exam requirements for a verified personal sea-time record (RYA Yachtmaster Scheme Syllabus and Logbook, G158).
Exam note. The examiner will ask to see your logbook and your passage log and may ask about your log-keeping and passage records as part of the oral questions. Expect questions such as: what do you record, how often, how do you correct a mistake, and what would you do after a collision.
Why Keep a Log?
A well-kept log is the yacht's memory. It has four functions:
- Navigation. If the GPS or electrics fail, the last logged position, course, speed and log reading let you work up a dead reckoning or estimated position straight away. A log that is hourly and complete is the backup for every electronic system aboard.
- Safety and handover. The oncoming watch can see what has happened: barometer trend, traffic seen, sail changes, problems. The skipper can see the state of the boat at a glance.
- Evidence. After a collision, grounding, injury or loss, the log is contemporaneous documentary evidence. Courts, the Marine Accident Investigation Branch (MAIB) and insurers give much more weight to records made at the time than to recollection afterwards.
- Experience. Logs record what the boat and crew did in which conditions, and support your sea time claims for RYA qualifications.
For private pleasure yachts in the UK there is no legal requirement to keep a log. Commercially operated small vessels under the MCA codes of practice must keep records of drills, safety equipment checks and other specified items. SOLAS Chapter V applies in part to pleasure craft (for example the duties to respond to distress messages, to plan the passage, to send danger messages and not to misuse distress signals), but its requirement to keep a record of navigational activities and incidents of importance to the safety of navigation (Regulation 28) is aimed at larger ships on international voyages. For any skipper, though, keeping a proper log is simply good practice and expected by the examiner. Insurers and investigators will ask for it, and the Master's duty of safe navigation under Regulation 34 (passage planning) is far easier to demonstrate if the log and plan exist.
Three Categories of Record
| Record | Purpose | Typical content |
|---|---|---|
| Official log or safety record | Legal and administrative events | Crew list and changes, drills, incidents, injuries, equipment defects affecting safety, births, deaths, disciplinary matters (on merchant ships) |
| Navigation (deck) log | Continuous record of the passage | Time, position, course, speed, log reading, weather, sail plan, engine, events |
| Maintenance records | Life history of systems and equipment | Service dates, next due, engine hours, defects and repairs |
On a merchant ship the Official Log Book is a statutory document whose format is set by regulations. On a yacht, "official" entries usually go in the back of the deck log or a separate safety record book. What matters is that they are made at the time and kept.
The Navigation Log
Content
A typical yacht deck log has these columns:
| Column | What to write | Example |
|---|---|---|
| Time | 24-hour clock, state the zone (UTC or local) at the top of the page | 1400 |
| Log reading | Distance through the water from the log | 132.4 |
| Course steered | Compass course, with T or C | 245C |
| Speed | Speed through the water, or SOG noted separately | 6.2 |
| Position | Lat and long, or bearing and distance from a charted object, with the method (GPS, visual fix, EP) | 50°10.2'N 005°02.6'W GPS |
| Wind | Direction and force | SW 4 |
| Sea, visibility | Sea state or wave height, visibility in miles | Moderate, 8 nm |
| Barometer | Pressure in hPa and tendency | 1014 falling |
| Sail or engine | Sail plan, engine on or off, rpm, engine hours | 1 reef, full genoa |
| Remarks | Events: traffic, marks passed, watch changes, sail changes, forecasts received | Lizard light abeam 4M |
The deck log entry format below is the standard used by most yachts. Every column should be filled in at every entry, even if only with a dash.
How Often?
- Offshore, open sea: at least hourly, and at every watch change.
- Near hazards, in restricted visibility, in traffic schemes and on approach to land: every 15 to 30 minutes, with positions marked on the chart as well.
- Additionally, whenever anything happens: alteration of course, sail change, engine start or stop, forecast received, mark passed, vessel sighted close, gear failure, injury.
Rule of thumb: if the electronics died now, could the next watch work out where you are within a mile using only the log? If not, you are not logging enough.
Worked Example: Using the Log for an EP
At 0300 the log shows: position 49°50.0'N 006°10.0'W (GPS), log 210.0, course steered 220°C, deviation 2°E, variation 2°W, wind NW 4. At 0400 the GPS fails. The log now reads 216.5.
- Distance run through the water: 216.5 minus 210.0 = 6.5 miles.
- True course: 220°C plus 2°E deviation gives 222°M, then minus 2°W variation gives 220°T.
- Leeway: the NW wind is on the starboard side and pushes the yacht to port (downwind), say 3°, so the water track is about 217°T.
- Plot 6.5 miles along 217°T from the 0300 position, then apply the tidal stream for the hour from the tidal atlas to get the 0400 EP.
Without the 0300 log entry, none of this would be possible.
Writing Good Entries
Facts, Not Opinions
Write what you measured or saw, not how it felt.
| Poor | Good |
|---|---|
| Weather getting worse | Wind backed SW to S, increased F4 to F6, baro 1012 falling 4 hPa in 3 hrs |
| Very rough | Rough sea, waves 2.5 to 3 m, occasional breaking crests |
| Poor visibility | Visibility 0.5 nm in fog, fog signal commenced, radar watch |
| Ship came too close | MV Ocean Star passed 0.3 nm ahead crossing port to starboard, CPA observed on radar 0.3 nm |
| Crew member hurt | J. Smith fell in galley, cut left forearm 3 cm, cleaned and dressed, no other injury |
Factual entries are useful to the next watch, are harder to dispute and show that the skipper was in control. Avoid admissions of blame, speculation or comment about other people. Record decisions and the reasons for them briefly: "Altered to 270°T to pass astern of tanker; CPA by radar 0.4 nm".
Correcting Errors
Never erase, tear out pages, use correction fluid or scribble over an entry. Any of these makes the whole log look as though it has been altered after the event and destroys its value as evidence.
The correct procedure:
- Draw a single line through the wrong entry so that it can still be read.
- Write the correct entry next to it.
- Initial and date the correction.
Use a pen, not pencil, for the log itself (pencil is fine for chartwork). Do not leave blank lines that could be filled in later. Write in time order. If an entry is added later, label it "late entry" with the time it was written.
Official Entries
Whether you call it an official log, a safety log or the back pages of the deck log, an offshore skipper should record:
- Crew list for each passage: names, nationality, passport numbers, next of kin, and any changes. Customs and immigration need this, and so does the coastguard if there is an incident.
- Safety briefing given, with date and who attended.
- Drills: MOB, fire, abandon ship, steering failure. Date, scenario, who took part, how long it took, what was learned.
- Incidents and accidents: injuries, near misses, collisions, groundings, damage, MOB.
- Medical treatment given, including medication from the first aid kit and any radio medical advice.
- Equipment defects affecting safety, and what was done about them.
- Communications with the coastguard: passage plans, Pan-Pan or Mayday traffic, Securité messages received that affected you.
These entries must meet the same standard: factual, objective, timely and permanent, with errors corrected only by a single line, correction and initials.
Other Records and Ship's Papers
A yacht on an offshore passage should carry a coherent set of papers, usually kept together in one waterproof folder. Examiners and Customs officers ask to see them.
| Document | Purpose |
|---|---|
| Certificate of registry (Part 1, Small Ships Register or other) | Proof of registration and nationality |
| Insurance certificate and policy | Cover, cruising limits, third-party liability |
| Ship Radio Licence | Call sign, MMSI, equipment; required for any radio |
| Skipper's and crew's passports | Immigration; next of kin |
| Operator certificates (SRC, Yachtmaster, ICC) | Evidence of competence |
| Evidence of VAT status | Needed for entering the EU and on return to UK |
| Passage plan and risk assessment | Evidence of planning under SOLAS V Reg 34 |
| Radio log and EPIRB registration | Evidence of safety arrangements |
| Customs notification (C1331 or NCP notification) | Arrival from abroad |
| Medical and drug register | Medicines, doses and treatments |
Keep copies, in paper and on a phone or tablet, of everything important. Photograph the pages of the log from time to time, because the original may be lost or damaged. An electronic log is acceptable as long as it records time and date automatically, cannot be edited without trace, and has a regular backup.
Watch and Rest Records
Record who was on watch, when they actually took over and handed over, and any deviation from the plan (for example someone called up early for a sail change, or the skipper on deck all night). A three-watch system of 4 hours on and 8 off gives each watch 8 hours of rest between watches, but real rest is less once you allow for meals, dressing and sail changes.
Why it matters: fatigue is a factor in many accidents. After a collision or grounding, an investigation will ask who was on watch and how much rest they had had. On commercial vessels there are statutory minimum hours of rest (for seafarers, at least 10 hours in any 24-hour period and 77 hours in any 7 days). Small commercial yachts must also manage hours under their operating code. Record actual times, not the planned rota.
During an emergency, appoint one person as recorder. Logging must continue: the timing of calls to the coastguard and of each action is exactly what everyone will want to know afterwards.
Incident Reports
After a significant event, write a fuller report as soon as practicable, while memories are fresh. A good structure:
- Date, exact time and position.
- Weather, sea state, visibility, tidal conditions.
- Sequence of events in time order.
- Persons involved and their roles.
- Injuries.
- Immediate actions taken.
- Medical treatment given.
- Communications with the shore (coastguard, TMAS, harbour authority) and times.
- Outcome, contributing factors, and measures to prevent it happening again.
The Marine Accident Investigation Branch (MAIB) investigates marine accidents in UK waters and involving UK vessels. The Merchant Shipping (Accident Reporting and Investigation) Regulations require reporting for commercial vessels, and are not a legal requirement for private pleasure craft, but the MAIB encourages voluntary reports from yachts and uses them to identify safety lessons. A death or serious injury should always be reported to the coastguard, who will involve the police and coroner as needed. Report to your insurer promptly, because most policies require notice of an incident and claim.
After a collision, Section 92 of the Merchant Shipping Act 1995 requires the master of each vessel, so far as can be done without danger to their own vessel and crew, to stay by the other vessel until they have ascertained there is no need of further assistance, to give the master of the other vessel the name of the vessel, port of registry and ports of departure and destination, and to render assistance to people on board. Failure to do so is an offence. Exchange details, record the other vessel's name and details in the log, and photograph any damage.
Maintenance Records
Maintenance records track every safety-critical item:
| Item | Typical interval |
|---|---|
| Liferaft | Service every 1 to 3 years as specified by the manufacturer |
| Hydrostatic release unit | Replace every 2 years (disposable type) |
| Pyrotechnic flares | Expire 3 to 4 years after manufacture |
| EPIRB and PLB battery | Replace by date shown, typically 5 to 10 years; HRU on EPIRB 2 years |
| Lifejackets | Annual service; check cylinders and auto-inflation heads before every passage |
| Fire extinguishers | Annual check, service as per manufacturer |
| Engine | Oil and filters at hours specified (often 100 to 250 hours), impeller annually |
The engine log should record running hours, oil and coolant checks, fuel used, oil and filter changes and any anomalies (smoke, vibration, overheating). Fuel consumption per hour lets you check how much is left independently of the gauge.
A pre-passage audit of these records is how you find the out-of-date flares and the overdue raft service before you need them, not after.
Your Personal Log for the Exam
The examiner will check your sea time before the Yachtmaster Offshore exam. Use the RYA logbook or a similar record and for each passage note:
- dates, vessel name and type, length, ports of departure and arrival;
- miles logged, days aboard, night hours;
- your role (crew, mate, skipper) and whether it was tidal waters;
- the skipper's signature.
Passages must be genuine and the details consistent. Distances and times should match the route, and the weather recorded should fit what actually happened. Examiners can and do check. Keep the navigation logs and passage plans from your qualifying passages too: they are evidence of your planning and decision making and good revision material.
Image: A.A. Buyskes, public domain, via Wikimedia Commons
Format has changed little in 240 years: time, course, distance, wind and remarks, in columns, in pen, with every entry made at the time.
Worked Example
Scenario. You are on a passage from Falmouth to La Coruña, 4 crew, and you take the 0400 to 0800 watch. Your entries:
| Time | Log | Course | Position | Wind | Baro | Remarks |
|---|---|---|---|---|---|---|
| 0400 | 98.2 | 205°T | 48°40.1'N 006°02.3'W GPS | W 4 | 1016 steady | Took over from A. Jones, 1 reef, full genoa |
| 0500 | 104.6 | 205°T | 48°34.3'N 006°06.0'W GPS | W 4 | 1015 | Ship lights to starboard, passed 2 nm astern |
| 0600 | 110.9 | 205°T | 48°28.6'N 006°09.6'W GPS | WSW 5 | 1013 | Rolled genoa to 70%, Navtex gale warning for Biscay later |
| 0700 | 116.8 | 210°T | 48°23.2'N 006°13.6'W GPS | WSW 5 | 1012 | Altered to 210°T for better sea angle, all crew briefed on gale warning |
| 0800 | 122.5 | 210°T | 48°18.2'N 006°17.8'W GPS | SW 6 | 1010 falling | Handed over to M. Lee, 2nd reef taken in |
Check: between 0400 and 0500 the log advanced 6.4 miles. The latitude decreased 5.8 minutes (5.8 miles south) and longitude increased 3.7 minutes west, which at 48.6°N is 3.7 x cos 48.6° = about 2.4 miles west. That gives a track of about 202°T over 6.3 miles, consistent with the course and log. The barometer fell 6 hPa in four hours, a clear indication of the coming gale, which matches the forecast. A reader can see exactly what happened and why.
Retention and Legal Status
A log has weight as evidence because it is made at the time by the person responsible. Keep logs, passage plans, radio logs and maintenance records for at least several years, and longer after any incident. Claims, inquests and insurance disputes can arise long after the event. Do not discard the log after an accident, do not add entries to the page afterwards except marked as late entries, and keep original pages if the log is bound and the incident is serious. Entries should be consistent between the navigation log, the radio log, the chart (record the plotted positions and keep the chart if there is an incident) and electronic records. Contradictions raise suspicion.
Exam Tips
- Bring your logbook, your passage log and your qualifying passage records. Keep them neat and complete.
- Expect to be asked what you log and how often, and how you correct a mistake. Describe the single line, the correction and your initials.
- Practise a complete log entry from memory.
- Be ready to explain what you would do after a collision, a man overboard or an injury, including log entries and reports.
Deck Log Entries in Practice
What to record at each position entry
A good hourly entry lets someone else reconstruct the passage with no other information. A typical line contains: time (state UTC or zone), log reading, position (latitude and longitude, or bearing and distance from a named object), course steered (compass and True), speed through the water and over the ground (SOG), wind direction and force, barometer in millibars (hectopascals), sea state and swell, visibility, cloud, sails set or engine hours, and remarks. The barometer is the key: a fall of 6 mb or more in three hours is a gale indicator, and only a log will show you the trend in time to act.
Worked example: a four-hour sequence of entries
Consider a yacht leaving Poole for Cherbourg. Entries might read as follows.
| Time | Log | Position | Course T | Wind | Baro | Remarks |
|---|---|---|---|---|---|---|
| 1000 | 0.0 | Poole Fairway buoy abeam 0.2M | 170 | SW 4 | 1016 | Departed, 1 reef, genoa, visibility good |
| 1100 | 6.1 | 50 31.2N 001 55.0W (GPS) | 175 | SW 4 | 1015 | Crew A seasick, taken off helm |
| 1200 | 12.0 | 50 25.2N 001 53.5W (GPS) | 175 | SW 5 | 1013 | Rain showers, second reef in |
| 1300 | 17.8 | EP only, GPS lost signal | 175 | SW 5-6 | 1010 | Fall of 6 mb in 3 hours, plan to divert to Alderney |
The 1300 entry shows the value of recording both observation and decision. It also shows the discipline of marking an estimated position as EP so that the next person knows its status.
Distance run and the log factor
The log reading gives distance through the water. Distance over the ground is different whenever there is a tidal stream. To find the log error (calibration), run a measured distance over a known tidal condition, or a slack-water run between two marks, and compare the log reading with the true distance. If the log reads 10.4 M for a known 10.0 M, the log overreads by 4 percent. Record the correction in the log book and apply it to every distance when plotting an EP.
Electronic logs and backups
Electronic logbooks and navigation apps record track and instruments continuously, which is valuable evidence, but they do not replace a written log. Batteries fail and software crashes. The common standard in a survey or inquiry is that a paper log should be kept as the primary record whenever the vessel is under way beyond the harbour limits, with electronic data as a back-up and cross-check.
Legal significance: what a log is evidence of
Under the Merchant Shipping Act 1995 and the Merchant Shipping (Official Log Books) Regulations, an official log book is mandatory on commercial vessels. A private yacht is not required to keep one, but a properly kept log is evidence in a Marine Accident Investigation Branch (MAIB) inquiry, in an insurance claim, in a Court of Inquiry after a collision (to demonstrate a good lookout, speed and COLREGs compliance), and in a salvage claim. If the log is missing, incomplete or visibly altered, the court and the insurer are entitled to draw adverse conclusions. After any incident, do not alter the log, secure it, and photograph the pages.
Key abbreviations used in logs
Use standard abbreviations: DR (dead reckoning), EP (estimated position), CTS (course to steer), COG and SOG (course and speed over ground), HDG (heading), VAR and DEV (variation and deviation), CTW (course through the water), WP (waypoint), XTE (cross-track error), AIS, VHF Ch (channel), ETA/ATA (estimated and actual time of arrival), UTC/BST. Define any non-standard abbreviation on the first page so the log remains readable by others.
Common Mistakes
- Gaps in the log during busy or bad-weather periods, which is exactly when it matters most. Appoint a recorder.
- Opinions instead of measurements: "rough", "bad", "too close".
- Erasing or obliterating mistakes, which makes the log look tampered with.
- Not recording the method of position fixing, so nobody knows whether a position is GPS, a fix or an EP.
- Logging the planned watch rota rather than actual hours.
- No time zone stated, making times ambiguous after crossing zones or the change to summer time.
- Not keeping maintenance dates, so flares or the raft service lapse unnoticed.
- Inconsistent personal logbook entries for the exam: distances that do not match the route or missing skipper signatures.
Summary
- The log is the yacht's memory: it supports navigation if electronics fail, handovers, legal evidence and your qualification claims.
- Keep three types of record: navigation (deck) log, official or safety record, and maintenance records.
- Log at least hourly offshore and every 15 to 30 minutes near hazards, plus every event.
- Write facts and measurements, not opinions. State the method of fixing and the time zone.
- Correct mistakes with a single line, the correction alongside and initials and date. Never erase.
- Record crew lists, drills, incidents, medical treatment, defects, actual watch hours.
- Write a structured incident report after any significant event.
- Your personal sea time record must be accurate, consistent and signed.
Check Your Understanding
1. Give three reasons for keeping a navigation log offshore.
Answer: To be able to work up a DR or EP if electronics fail, to hand over the watch with full information, to provide contemporaneous evidence for investigations and insurers, and to record experience.
2. How often should you log offshore, and when should you log more frequently?
Answer: At least hourly and at every watch change offshore. Every 15 to 30 minutes near hazards, in restricted visibility, in traffic schemes or approaching land, and whenever any event happens.
3. Rewrite this entry factually: "Weather turned nasty, very rough sea".
Answer: For example: "Wind backed SW to S, increased F4 to F6, baro 1009 falling 3 hPa in 2 hrs, sea rough, waves about 2.5 m".
4. You wrote 245°T in the log instead of 254°T. How do you correct it?
Answer: Draw a single line through 245°T so it remains readable, write 254°T alongside, and initial and date the correction. Never erase or obliterate.
5. Name five things that should be recorded in the official or safety part of the log.
Answer: Any five of: crew list and changes, safety briefings, drills, incidents and accidents, injuries and medical treatment, equipment defects affecting safety, communications with the coastguard, births or deaths, disciplinary matters (commercial).
6. Why record actual watch and rest hours rather than the planned rota?
Answer: Because the actual hours show whether the crew were fatigued. Investigations after an accident will ask how much rest the watchkeeper had had, and commercial vessels must meet minimum rest requirements.
7. List the main headings of an incident report.
Answer: Time and position; weather and conditions; sequence of events; people involved; injuries; immediate actions; medical treatment; communications with shore; outcome, contributing factors and preventive measures.
8. The log shows 0300 log 210.0 and 0400 log 216.5, course 220°T, and GPS fails at 0400. What distance do you plot for the DR, and what else is needed for an EP?
Answer: 6.5 miles along 220°T (adjusted for leeway) gives the DR. For an EP you also apply the tidal stream for the hour.
9. What does the examiner check in your personal logbook before the Yachtmaster Offshore exam?
Answer: That the sea time requirements are met (50 days, 2,500 miles, 5 days as skipper, 5 passages over 60 miles including 2 overnight and 2 as skipper) and that entries are consistent, realistic and signed by the skippers concerned.
10. What does the Master of a vessel involved in a collision have to do under the Merchant Shipping Act 1995?
Answer: So far as possible without danger to their own vessel and people, stay by the other vessel until satisfied that no further assistance is needed, give the master of the other vessel the name of the vessel, her port of registry and the ports of departure and destination, and render assistance to people on board. Record the details in the log.
11. Why is a pencil entry or an erased entry a problem in a log?
Answer: It can be altered easily and makes the log look as though it was changed after the event. A log used as evidence has to be contemporaneous, in pen, and corrected only by a single line, the correction and initials.
12. Name six documents you would expect to find in the ship's papers.
Answer: Any six of: certificate of registry, insurance certificate, Ship Radio Licence, passports, operator certificates, VAT evidence, passage plan, radio log, EPIRB registration, Customs notification, medical and drug register.