For years I anchored the way most of us were taught: find a sheltered bay, motor up into the wind, let the hook go where it looked deep enough, and back down hard to set it. It works. It also, I eventually understood, can do real damage to the seabed underneath, and on parts of the French coast that careless habit is now both an ecological problem and a legal one. Changing how I anchor cost me almost nothing and made me a better sailor for it. Here is what I learned.
What anchoring actually does to the bottom
An anchor and chain are blunt instruments. The anchor digs a hole when it sets, the chain sweeps an arc across the bottom as the boat swings, and on retrieval the whole lot drags up whatever it has bitten into. On sand, mud or gravel, the seabed heals fast and nobody worries. On a living seabed, it is a different story.
The seabed that matters most in France is Posidonia oceanica, a seagrass found only in the Mediterranean. It forms dense underwater meadows from about 1 metre down to 40 metres in clear water, and it is the foundation of the whole coastal ecosystem: nurseries for fish, oxygen for the water, sediment held in place against erosion. It is sometimes called the lungs of the Mediterranean for a reason.
The problem is how slowly it grows: a matter of centimetres a year. An anchor and chain can rip out a patch of meadow in seconds that took a century or more to grow, and a single scar can take decades to recover, if it recovers at all. Multiply that by every boat in every popular bay across a summer and the damage is enormous. That is the background to France's tightening rules, which I cover in detail in my guide to the Posidonia anchoring ban in France.
The rules now carry real teeth
This is no longer just good manners. France has made it law. Vessels over 24 metres are banned from anchoring on Posidonia, and the penalties are severe: fines reaching 150,000 euros, with the most serious cases carrying the threat of prison and a navigation ban in French waters.
The 24-metre threshold is where the hard law currently bites, and successive decrees have extended protected zones along the Cote d'Azur, the Provence coast and around Corsica, with new restricted areas added year on year. But the direction of travel is clear, and smaller boats are increasingly expected to follow the same principle. Some specific bays now ban anchoring outright for all sizes, or require you to use installed mooring buoys. The boundaries change, so the only safe assumption is that any Med bay with a seagrass bottom may be regulated, and you should check before you drop. The wider picture of where you can and cannot anchor is in my notes on anchoring rules on the Cote d'Azur for 2026.
Reading the bottom before you drop
The single most important skill is reading the seabed by eye and by chart, because the whole game is to put your anchor on sand and keep it off the grass.
By eye, in clear Mediterranean water, it is genuinely easy once you train yourself. From the bow, with polarised sunglasses, the contrast is stark:
- Pale, bright, sandy patches are clean bottom and good holding
- Dark green to brown patches, often with a visible texture like a lawn seen from above, are seagrass. Stay off them
- A mottled mix means broken meadow with sand channels, aim for the clear lanes
Send someone to the bow to con you onto a sand patch while you handle the helm and the windlass. In the Med's clarity you can usually see well enough to drop precisely. In murkier Atlantic or Channel water you rely more on the chart and the echo sounder, but Posidonia is a Med species, so the seagrass worry is largely a southern one.
The apps that map the seabed
You do not have to guess. Two tools have changed this completely.
The Donia app, developed by Andromede Oceanologie and launched back in 2013, maps the Mediterranean seabed in detail, showing exactly where the Posidonia meadows lie and where the sand is. You see your boat's position over a simplified seabed chart and pick a sandy spot to anchor. For anyone cruising the French Med it is close to essential.
Navily, the anchorage-review app many cruisers already use for finding bays and reading other sailors' notes, also flags Posidonia at anchorages and lets users report seagrass directly, so the seabed type shows up on the anchorage page. Between the two you can plan an anchorage before you arrive and know whether there is sand to drop on or whether you should be looking for a buoy instead.
Mooring buoys and the alternatives
In the most sensitive and most popular spots, the answer is increasingly not to anchor at all but to pick up an installed eco-mooring. These are fixed to the bottom in a way that does not drag, and many of the marine parks and protected bays have laid fields of them precisely so boats can stop without scarring the meadow. Some are free, some carry a modest fee, and in the busiest places they go early in the day, so arrive in good time.
Where there is no buoy and no sand, the honest answer is sometimes to move on to a different bay. That is a hard discipline on a hot afternoon when you want to swim, but it is the right one.
A practical low-impact routine looks like this:
- Check the app and the chart for seagrass before you commit to a bay
- Look for a laid mooring buoy first, and use it if one is free
- If anchoring, con onto a clean sand patch from the bow, never drop blind onto a dark bottom
- Use enough scope to hold, but be aware that a longer swing sweeps a wider arc, so balance security against the area you disturb
- Retrieve cleanly, motoring up over the anchor rather than dragging it sideways out of the bottom
It is not just the Med
Seagrass is the headline, but low-impact anchoring is a habit that travels. Atlantic and Channel waters have their own sensitive habitats, eelgrass beds, maerl grounds and shellfish beds among them, and the same principle applies: know what is under you, prefer clean holding ground, and disturb as little as possible. The wildlife you cross on passage, the dolphins and the feeding tuna I write about in my notes on the Bay of Biscay food chain, all ultimately depend on healthy seabed habitats somewhere in the system.
The payoff
Anchoring well costs you nothing but a little attention. You read the bottom, you drop on sand, you use a buoy where one exists, and you move on where the holding is bad for the seabed. In return you keep the meadows that make the water clear, the fish abundant and the snorkelling worth doing in the first place, the kind of in-water life I describe in my guide to snorkelling the Calanques and Med marine life.
The old way of anchoring treated the seabed as a parking space. The better way treats it as somewhere alive that you are a guest in. Once you make the switch, dropping blind onto a dark patch starts to feel as wrong as dumping rubbish over the side. Read the bottom. Drop on the sand. Leave it as you found it.
