The tide is the most reliable force a coastal sailor works with — and the most unforgiving when ignored. These guides move from the physics of tidal generation through to specific hazards like overfalls, tide races, and drying harbours. Whether you are timing a tidal gate passage or choosing an anchorage in a drying harbour, understanding the tide is non-negotiable seamanship.
Understanding Tides: Physics, Patterns, and Prediction
Spring vs neap cycles, diurnal vs semi-diurnal patterns, chart datum, the rule of twelfths, and how to read tide tables — including secondary port corrections.
- Spring vs neap tides explained
- Rule of twelfths for hourly heights
- Reading secondary port corrections
Using Tides to Plan Passages
Timing departures on a fair tide, the economics of tide assistance, tidal gates at headlands and straits, bar crossings, and the spring-neap calendar.
- 1–2 kt push = 10–20% fuel saving
- Portland Bill, Pentland Firth, Cape Cod Canal
- Wind against tide = steep seas
Reading Tidal Streams and Tidal Stream Atlases
Tidal diamonds on Admiralty charts, interpolating for intermediate states, vector plotting the tide triangle, electronic overlays, and pilotage in tidal waters.
- Springs vs neaps interpolation
- Drawing the tide triangle
- Navionics and C-MAP current overlays
Tidal Hazards Every Sailor Must Know
Overfalls and tide races, drying harbours, grounding on a falling vs rising tide, tidal bores, current set onto lee shores, and safe anchoring in tidal zones.
- Portland Race, Raz de Sein, Race Rocks
- Falling vs rising tide grounding risk
- Drying harbour approach and berthing
About These Guides
These are editorial resources for educational purposes. Tidal predictions are produced from harmonic constants and are accurate under standard conditions, but actual water levels can deviate due to storm surge, strong winds, and river discharge. Always consult current official tide tables (NOAA, UKHO, or your national hydrographic authority) and up-to-date charts before making navigational decisions based on tidal data. See also the cruising guides and the marina directory.