Is my anchor dragging? How to tell, and what to do in the first two minutes
Most dragging anchors announce themselves quietly. How to read the signs, check them fast, and get the boat back under control without making things worse.
In this piece
A dragging anchor rarely makes a scene at first. The boat just stops behaving like the boats around her. She lies a little more beam on, the lights ashore line up differently, the chain makes a sound it did not make an hour ago. By the time it is obvious you have usually lost a few boat lengths, and in a tight anchorage that can be all the room you had.
This is how we check, and what we do in the first couple of minutes once we are sure. None of it is clever. It just works much better when you decided it in daylight.
Signs your anchor is dragging
No single sign proves it. Boats swing differently on chain and on rope, a fin keel sails around more than a long keel, and a catamaran catches the wind like nothing else in the bay. What you are looking for is change, and ideally two signs that agree.
The transit has opened
When you anchor, pick two things ashore that line up from the cockpit: a light and the hill behind it, the corner of a building and a tree. That is a transit. As the boat swings it will wander a little and come back. If it walks steadily one way and stays there, the boat has moved. Two compass bearings to fixed objects do the same job, but a transit is quicker in the dark and needs nothing except your eyes.
She is lying beam on
A boat held by her anchor lies roughly head to wind, nodding through her swing. A boat that is dragging tends to fall off and lie with the wind on the beam, because nothing is pinning the bow any more. If you come up and every boat in the bay points one way and yours points another, look harder.
The chain grumbles
Put a hand on the chain forward of the snubber. Chain that is holding is either taut and quiet or slack and quiet. An anchor bouncing across the bottom sends a rumble up the links that you can feel in your palm, sometimes as short jerks. It is one of the most reliable signs there is and the least used, because it means going forward in the rain.
The depth is wrong
Note the depth when the boat settles. If the sounder now shows a couple of metres more than anything you saw during the swing, or the bottom is shoaling toward a beach that is downwind of you, find out why before you go back to bed.
The track has stopped drawing arcs
An anchored boat leaves a GPS track that looks like scribble on a fan: arcs back and forth, all on the downwind side of the anchor. A dragging boat draws a line. After a few nights of looking at tracks, that line is the most obvious thing on the screen, and it is exactly what an anchor alarm watches for so you do not have to.
The neighbours have moved
The least reliable of the lot, because they swing too and they may be the ones dragging. Treat it as a prompt to check the others, never as proof on its own.
Check before you act
At two in the morning, an alarm plus a gust plus a boat that suddenly looks close can add up to a panic that does more damage than the drag. Give it twenty seconds. Look at the transit, put a hand on the chain, look at the track. If two of them say you are moving, you are moving.
If an alarm went off and everything else is calm, look at the radius before you blame the anchor. A wind shift can swing you to the far side of a circle that was drawn too tight, and a phone that was set while you were still motoring back on the chain may think the anchor is somewhere it is not. We wrote a whole piece on setting an alarm radius that will not cry wolf.
What to do in the first two minutes
This is the order we work in. Crews differ and boats differ, but the order matters more than the details.
- Shoes, light, life jacket. A wet deck at night in a blow is where people get hurt. Thirty seconds for a head torch (red if you have one, so you keep your night vision) and a life jacket is not wasted.
- Start the engine, then look at the water. Before anything else, make sure you can motor. Check that cooling water is coming out of the exhaust. Then look for ropes in the water. The dinghy painter is the classic, and a line round the prop turns a nuisance into an emergency.
- Take the load off the anchor. Motor gently into the wind, just enough to hold your ground. That stops the drift and makes the chain easy to bring in. Whoever is at the bow points along the chain so the helm never drives over it.
- Decide: more chain, or start again. With plenty of water and plenty of room downwind, and a slow drag, letting out more scope will sometimes let the anchor dig in. If the anchorage is tight, the wind is still building or you are already close to something, bring it up.
- Look at the anchor as it comes up. A ball of weed on the tip, a plastic bag, somebody’s old mooring chain, a slab of rock caught in the fluke. One look tells you more about the bottom than the chart did, and none of those problems is solved by more chain. Clear it before it goes down again.
- Re-anchor with more room and more scope. Move further from whatever you were drifting toward and let out more than last time. Then set it properly: let the boat fall back, snub the chain, build up astern slowly and hold it while you watch a transit. If it holds hard astern, it will hold the night. There is more on that in how much chain to let out.
If someone else is dragging down on you, the same list applies with one addition: wake them up. Horn, a strong torch on their coachroof, a call on the VHF if you know the boat’s name. Fenders out, and if the hulls are going to meet, fend off with a boathook or a fender, never with a hand or a foot.
Why anchors drag in the first place
The big one is scope. Short chain lifts the shank and pulls the anchor up out of the bottom instead of along and into it. It is also the cheapest problem on this list to fix.
Next comes an anchor that was never really set. Lying on its side on hard sand, it will hold in a light breeze and let go in the first proper gust. Then the bottom itself: weed, a thin skin of sand over rock, soft mud, Posidonia seagrass. In the Mediterranean, look for the pale patches of sand between the dark seagrass and drop there. Our guide to choosing an anchorage goes into what to look for.
Wind shifts catch people out because the anchor was set for a pull from one direction. When the wind swings round overnight the boat pulls from the other side. Most modern anchors turn and reset. Some pull out first, and a few collect a ball of weed on the way round that stops them biting again.
And then there is snatching. In gusts the boat sails around her anchor and fetches up with a jerk at each end. A snubber, a length of stretchy nylon between the chain and a bow cleat, takes most of that shock out before it reaches the anchor.
Make it someone else’s job to notice
Every sign above needs a person awake to see it. That is fine for a lunch stop and hopeless for a night when the whole crew is asleep. Anchor watch on a cruising boat used to mean taking turns in the cockpit with a flask. These days it mostly means the phone.
A good alarm does not replace any of the checks. It tells you when to do them. When it goes off you still go up, look at the transit, feel the chain and decide. The difference is that you are deciding with twenty seconds of warning instead of twenty metres.