Navigation & tides

Worked tide examples

The tidal questions in the Day Skipper and Yachtmaster exams, each worked through step by step with a tide curve. Check your own numbers in the tide calculator.

  1. 01How to Calculate the Height of Tide at a Given TimeHigh water is at 0930 (5.3 m) and low water at 1530 (0.9 m). What is the height of tide at 1230?
  2. 02How to Work Out What Time the Tide Reaches a Given HeightLow water is at 0410 (1.1 m) and high water at 1010 (4.9 m). You need 3.0 m of tide to leave your berth. When can you…
  3. 03How to Work Out the Depth of Water from a Charted DepthYou are over a charted depth of 2.4 m at 1230. HW was 0930 (5.3 m), LW is 1530 (0.9 m). How deep is the water, and wh…
  4. 04Under-Keel Clearance: When Is There Enough Water to Get In?A harbour entrance has a charted depth of 0.6 m over the bar. Your draught is 1.8 m and you want 0.5 m under the keel…
  5. 05Drying Heights: How to Work Out When You Can Cross a Drying BankA channel dries 1.4 m (charted as 14 underlined). Your draught is 1.2 m and you want 0.4 m clearance. LW 1310 (0.7 m)…
  6. 06Will My Mast Fit Under the Bridge? Air Draught and Bridge ClearanceA bridge has a charted clearance of 12.0 m above HAT, which is 5.8 m at this port. Your mast top is 13.5 m above the …
  7. 07Anchoring: How to Work Out the Depth at Low Water and How Much ChainYou arrive at an anchorage at high water, 1400 (4.6 m). LW is at 2000 (1.0 m). Your echo sounder (reading below the w…
  8. 08How to Work Out if It Is Springs or Neaps from the Tidal RangeToday's tides at a standard port are HW 5.3 m and LW 0.9 m. The port's MHWS is 5.5 m, MHWN 4.4 m, MLWN 2.2 m and MLWS…
  9. 09How to Work Out Tidal Stream Rate from a Tidal DiamondThe table for tidal diamond A gives, at HW+2: direction 075°T, spring rate 2.4 kn, neap rate 1.2 kn. Today's range at…
  10. 10How to Calculate the Time of High Water at a Secondary PortHW at the standard port is 0930 UT. The secondary port's time differences for high water are −0010 when standard port…
  11. 11How to Calculate the Height of High Water at a Secondary PortToday's HW at the standard port is 5.3 m. The standard port's MHWS is 5.5 m and MHWN 4.4 m. The secondary port's heig…