Module 11 - Tides & Tidal Streams
Tidal streams and gates in Yachtmaster passage planning
What you will learn
Translate stream direction, strength and change into a timed gate, course-control plan and abort decision for a coastal passage.
A tidal gate is not merely the moment a stream turns. It is a route point whose usable window depends on vessel speed, stream, sea state, depth and room to recover.
Tidal stream changes course made good, speed over ground and passage time. A fair stream can reduce duration; a foul stream can prevent a yacht making useful progress through a narrows or past a headland. Wind opposing stream can steepen and shorten waves, especially at races, bars and headlands.
A tidal gate is a point where timing relative to the stream or height is critical. Convert the relevant tidal phase into a clock time from the named reference, then work backwards using a conservative speed over ground. Add set-up, traffic, sea-state and recovery time.
During pilotage, monitor cross-track trend, speed over ground, depth and the next safe holding or turn-away point. Recalculate when actual stream or progress differs materially from the plan; do not press on because the original gate time looked achievable.
| Gate input | Planning question | Control |
|---|---|---|
| Reference | Which HW and time basis? | Label the clock |
| Stream/height | When does the limit begin? | Latest clear time |
| Vessel | What conservative SOG applies? | Departure calculation |
| Sea state/traffic | What delay or risk is credible? | Contingency |
| Recovery | Where can the yacht hold or turn away? | Earlier abort |
Work backwards from the gate
Foul stream starts at 0950. The yacht must be clear 30 minutes earlier and needs 75 minutes from berth to gate in the expected conditions.
1. Set clear-by time
0950 - 30 minutes = 0920.
2. Calculate latest departure
0920 - 75 minutes = 0805 before any additional set-up allowance.
3. Brief the abort
Name the latest point at which slow progress triggers holding, turning away or the alternative route.
Sense check: A plan that departs at 0920 has confused the clear-by time with the leave-berth time.
Common mistake or limitation
- A fair-tide start does not guarantee a fair stream throughout a long leg; check the hourly sequence.
- Wind against tide can worsen sea state, but the severity depends on wind, water depth, stream, fetch and local geometry.
Recap
- Turn the tidal phase into a labelled clock time.
- Work backwards using conservative progress and contingency.
- Monitor and use an earlier abort when reality departs from the plan.
Optional quick check
Section 10 of 13
A gate must be clear by 0920 and the route takes 75 minutes. What is the latest unbuffered departure?
Sources and factual review
Reviewed 20 August 2026 - Compass Revision editorial review.
Use tidal streams inside a full passage
The tides module combines stream atlases, diamonds, secondary ports, gates, pilotage and conservative margins.