Dragging vs. Sailing Round the Anchor
Before you can act, you must correctly diagnose what is happening. A vessel sailing round the anchor swings in a predictable arc about a fixed point — the anchor. GPS positions describe a circle whose radius approximates scope deployed; bearings to fixed objects on the periphery of that arc change continuously but the vessel returns. A vessel dragging produces a progressive shift of that whole pattern: the arc migrates, bearings to shore objects change and do not return, and successive GPS positions show a track with a consistent set.
Detecting Drag
Visual/compass: Take two or more cross-bearings to fixed charted objects immediately on anchoring. Plot them. Repeat at frequent intervals, especially in deteriorating conditions. A bearing that opens or closes without oscillating is the classic tell.
Radar: Drop a parallel-index line or ERBL on a fixed radar-conspicuous target the moment you anchor. Any growth of distance or azimuth change that does not correct is drag.
GPS/ECDIS: The anchor-watch alarm on most chart-plotters draws a drag circle of chosen radius around the position at which you anchored. Understand its limitation — it triggers on ship's position, not anchor position, so it must be set generously enough to allow for normal swinging.
Feel and sound: Chain going taut in surges and a pronounced vibration or catenary lifting off the bottom are physical indicators. Running the machinery room telegraph from the anchor watch to detect through-hull transmission is seldom possible on a yacht, but the watch-keeper on deck should be sensitised to intermittent jerking of the cable.
Depth: A sounder trace showing shoaling is an urgent confirmatory sign — you are approaching the beach.
Action as Master
- Verify — confirm drag against at least two independent methods before committing to action. Do not cause collision by premature manoeuvring.
- Alert — call all hands, engines to immediate readiness, notify the owner/bridge team.
- Engine assistance — motor up to reduce cable tension and allow the anchor to re-set. Do not short-stay and try to drag the anchor back; motor toward the anchor, then let the cable drop taut gently.
- Veer more cable — if swinging room permits, additional scope dramatically increases holding power (roughly as the square of scope). This is often the fastest fix in open anchorages.
- Second anchor — deploy if the dragging anchor will not re-set and swinging room permits; place it so that both cables lead forward with a divergent angle.
- Weigh and re-anchor — choose a better position or better ground; re-assess the charted bottom type.
- Weigh and seek shelter or sea room — if conditions preclude safe re-anchoring, the duty is to get the vessel to safety; do not anchor in a situation where drag will place the vessel in danger.
- Notify — if dragging into a fairway, VTS or port control must be informed; if collision is imminent with another anchored vessel, sound signals under Rule 34(d).
Record all actions, times, positions and reasons in the deck log. That record protects you legally and is evidence of the seamanlike management of the vessel.