What does the "Rule of Twelfths" help determine?

The "Rule of Twelfths" is a practical, simplified method utilized to estimate tidal heights at various points in the tidal cycle. It breaks down the tidal movement into twelve equal parts, helping mariners understand changes in water levels during tidal phases. Essentially, during a tidal cycle, the first hour after high or low tide sees approximately one-twelfth of the total tide height change; the second hour sees about two-twelfths, and this pattern continues until the tide reaches its next high or low mark. This rule assists watchstanders in predicting how much water will be available and the timing of tidal changes, which is crucial for safety when navigating in shallow areas or planning boat activities.

Understanding tides and currents is vital for safe navigation, especially in coastal areas where tidal influences can be significant. By using the Rule of Twelfths, mariners can better predict the behavior of tides and adapt their plans accordingly. The focus on tides and currents distinguishes this rule from considerations related to weather conditions, vessel speed, or water temperature, which are governed by other factors and do not relate to the tidal cycle's dynamics.