How to Tell If Your Anchor Is Dragging: 5 Warning Signs Every Sailor Should Know

What Is Anchor Dragging?

Anchor dragging occurs when your anchor loses its grip on the seabed and your boat starts to drift from its anchored position. This can happen gradually — moving just a few meters at first — or suddenly, especially during a wind shift or increasing seas.

The danger is real: a dragging anchor can lead to grounding on shore, collision with other boats, running onto rocks, or drifting into shipping lanes. Many maritime incidents occur at night when the crew is asleep and unaware their anchor has let go.

The 5 Warning Signs of Anchor Dragging

1. Changing Bearings to Fixed Objects

This is the oldest and most reliable method. When you first set your anchor, note the bearings (angles) to fixed objects on shore — a lighthouse, a building, a distinctive rock formation, or another landmark. Take bearings on at least two objects that are roughly 90 degrees apart.

Periodically check these bearings. If the angle to a fixed object changes significantly, your boat is moving and your anchor may be dragging. This method works well during the day but is obviously limited at night.

2. Increasing Distance from Shore or Other Boats

If you notice that the shoreline appears farther away than when you anchored, or that the distances between your boat and neighboring boats have changed, investigate immediately. When multiple boats are anchored in the same area, all boats should swing in roughly the same direction with the wind and current.

If your boat's position relative to others is different from what you expected, there's a good chance your anchor — or theirs — is dragging.

3. GPS Position Shifting

Modern GPS provides an exact measure of whether your boat has moved. By dropping a waypoint at your anchor position or using a dedicated anchor alarm app, you can continuously monitor your distance from the anchor point.

A properly set anchor will allow some movement — the boat swings in a circle around the anchor based on wind and current. But the center of that circle (the anchor point) should remain constant. If your GPS shows the anchor point drifting, the anchor is dragging.

Pro tip: An anchor alarm app like Safety Anchor Alarm automates this completely. Set your safe radius and the app will wake you up the moment your boat moves outside the zone — even at 3 AM.

4. Chain or Rode Tension Changes

A well-set anchor typically maintains consistent tension on the rode (chain or line). Pay attention to how your chain feels and sounds:

• Sudden jerking or snatching — the anchor may be skipping across the bottom
• Complete slack followed by sudden tension — the anchor is intermittently catching and releasing
• Vibration through the chain — the anchor may be dragging across rock or hard bottom
• Unusually slack chain — the boat may have drifted over the anchor

You can also feel the chain with your hand (carefully). A firmly set anchor transmits steady tension with gradual changes as the boat swings. Erratic behavior suggests problems.

5. Depth Sounder Readings Changing

If you noted the water depth when you anchored and the depth starts to change significantly (either shallower or deeper), your boat is moving to a different part of the seabed. Decreasing depth is particularly alarming as it may mean you're drifting toward shore or a shoal.

Some sailors set a shallow water alarm on their depth sounder as an additional safety measure alongside their anchor alarm.

What Causes Anchors to Drag?

Understanding the root causes helps you prevent dragging in the first place:

• Insufficient scope — the most common cause. If you haven't let out enough chain relative to the water depth, the pull on the anchor is too vertical, reducing holding power. Use our anchor scope calculator to get the right ratio.
• Poor holding ground — rock, kelp, thick weed, or very hard sand can prevent the anchor from setting properly
• Wind shifts — a 180-degree wind shift can pull the anchor out of the seabed as the boat swings around
• Increasing wind or wave action — heavier loads on the anchor may exceed its holding capacity
• Wrong anchor type — different anchors perform differently on different bottoms (sand, mud, rock)
• Anchor not properly set — if you didn't reverse firmly enough to set the anchor, it may pull free under load
• Tidal changes — rising water effectively reduces your scope ratio, potentially to an unsafe level

How to Prevent Anchor Dragging

1. Use adequate scope. Aim for at least 7:1 in normal conditions and 10:1 in heavy weather. Always account for freeboard height and tidal changes.
2. Set the anchor properly. After dropping the anchor and paying out chain, reverse the engine gently at first, then firmly, to dig the anchor in. Watch your GPS or transit bearings to confirm the anchor is holding.
3. Check the seabed. Use your chart to identify the bottom type. Sand and firm mud offer the best holding. Avoid thick weed, rock, or coral if possible.
4. Use an anchor alarm. The most reliable overnight protection. An app like Safety Anchor Alarm monitors your GPS position continuously and wakes you if anything changes.
5. Monitor the weather forecast. If conditions are expected to deteriorate, consider moving to a more sheltered anchorage or increasing scope.
6. Leave an anchor light on. Required by maritime regulations and helps other vessels see you, reducing collision risk if your anchor does drag.

What to Do If Your Anchor Is Dragging

If you determine that your anchor is dragging, act quickly but calmly:

1. Start the engine immediately. Having the engine running gives you control of the situation regardless of what happens next.
2. Assess the situation. How fast are you dragging? Is there immediate danger (shore, other boats, rocks)?
3. Let out more chain. If you have room to drift and more chain available, increasing scope may allow the anchor to reset on its own.
4. Motor slowly toward the anchor to reduce load, then let the chain tighten again to reset.
5. Re-anchor if necessary. If the anchor won't hold, retrieve it completely and move to a new position with better holding ground or more shelter.
6. Consider a second anchor. In deteriorating conditions, deploying a second anchor at a 45-degree angle can significantly increase holding power.

The Bottom Line

Anchor dragging is preventable with good seamanship: adequate scope, proper setting technique, awareness of the seabed, and vigilant monitoring. But even the best sailors can face unexpected conditions.

The single most effective safety measure for overnight anchoring is a reliable anchor alarm. While traditional anchor watches require someone to stay awake, Safety Anchor Alarm monitors your GPS position continuously and sounds a loud alarm the moment your boat drifts outside your safe zone — giving you time to react before a minor drag becomes a serious incident.