What is the procedure for anchoring a ship?

Anchoring a ship safely follows a clear sequence of seamanship from preparation through to standing anchor watch, and skipping steps in that sequence is how anchors drag, cables part, or ships collide with others already anchored. Before arrival, the officer of the watch or navigating officer selects a position with good holding ground, suited to the anchor and seabed type, adequate depth for the ship's draught at all states of tide, some shelter from the prevailing wind and sea, and enough swinging room around the anchor to clear other vessels, charted dangers and shallow water throughout the stay, then calculates how much cable to use, commonly worked out as a multiple of the water depth, more in the region of five to six times depth or more in poor holding ground, strong wind or exposed anchorages, less in calm sheltered conditions.

The anchor party mans the forecastle in good time, checks the windlass, brake and cable are free and in working order, and confirms the anchor is clear to let go, while the bridge and forecastle maintain reliable communication throughout, by radio or an agreed set of hand and light signals. On approach, the ship is brought slowly toward the chosen position, normally heading into the wind or the tidal stream, whichever is dominant, so the ship's way can be checked accurately and the vessel will naturally lie back on its cable once anchored rather than riding over it; engines are used to bring the ship to a near stop, or a slight sternway, at the moment of letting go.

The anchor is then let go and allowed to run, or walked back under power of the windlass in deeper water or where a controlled drop is preferred, and cable is paid out under control to the calculated scope while the officer on the forecastle reports how the cable is growing, whether it leads ahead, astern or to a side, and whether it is coming taut and slack rhythmically as the anchor digs in, or remaining slack and dragging, all of which is relayed to the bridge. Once the cable is leading steadily in one direction and holding without further dragging, the ship is reported brought up, its position is fixed and logged, and the anchor ball or anchor lights required under the collision regulations are shown.

Through the stay, the bridge keeps a proper anchor watch, fixing the ship's position at regular intervals using bearings, radar ranges and GPS, watching for a change in the way the ship lies to wind and tide, an unusual cable angle, or a vibrating or jerking cable, all of which can indicate the anchor is dragging, and stands ready to veer more cable, use the engine to relieve strain, or weigh anchor and reposition if weather deteriorates or another vessel's swing brings a risk of collision.