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Essential Navigation module 4 of 10

Tides Basics

High water, low water, tidal height, tidal streams, and why tide matters before leaving.

high waterlow watertidal heighttidal stream

What to know for Tides Basics

Check whether there will be enough water and whether tidal stream will help or hinder the trip.

High water, low water, tidal height, tidal streams, and why tide matters before leaving. This module is mapped to the published course boundary for Essential Navigation and Seamanship Revision and written as an independent revision aid, not official training material.

Key Points

  • Tidal height affects clearance under the keel
  • Tidal stream affects speed and track
  • Harbours may have gates or depth limits
  • A simple tidal check belongs in every beginner plan

Last reviewed: 6 July 2026 by Compass Revision curriculum review

Source notes

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