The period around high water when a deep-draught ship has enough under-keel clearance to transit a channel or berth, or more broadly any time slot set by tide height or current. Ports publish tidal windows for the largest ships, pilots plan sailings around them, and marine contractors book cranes, divers and pours around them. Missing the window can mean waiting a full tidal cycle.
Tide window for the bulker closes at 1630, so pilot boards at 1400 or she waits till tomorrow.
Under-keel clearance rules add squat, wave response and a safety margin to the ship's draught, so a window depends on more than the predicted tide.
Also heard as
- tidal window
- tidal restriction
Related terms
Max flood
The peak strength of the flood current in a cycle, and the time it occurs; max ebb is the seaward equivalent.
Slack water
The short lull when a reversing current almost stops while it swaps between flood and ebb.
Agger
A double high water or double low water, where the tide peaks or bottoms out twice in quick succession.
Chart datum
The low-water zero that charted depths and tide table heights are measured from.