If you cruised the French Riviera or the Balearics last summer, you probably noticed it: fewer boats in the old favourite coves, more buoy fields, and rangers in RIBs actually stopping to check. Posidonia enforcement is no longer a paper threat. Fines have been handed out from Porquerolles to Formentera, and the rules keep tightening every season. Here is what the current framework actually says, how to read the seabed before your chain hits it, and where you can still swing on your own hook without risking a five-figure penalty.

Why Posidonia matters, and why enforcement got serious

Posidonia oceanica is not seaweed. It is a slow-growing flowering plant endemic to the Mediterranean, forming meadows that stabilise the seabed, oxygenate the water, and shelter a large share of the Med's juvenile fish. A meadow grows roughly one centimetre per year. A 10 kg anchor dragged across it for thirty seconds can rip out patches that took a century to form.

For years the response was educational: signs at the capitainerie, a leaflet in the pilot book. That changed around 2019 when France started issuing prefectoral decrees with real teeth, and the Balearic government began deploying patrol boats with underwater cameras. Today, in most of the western Med, anchoring on Posidonia is either explicitly banned or effectively banned by minimum-depth rules that push you off the meadow whether you know what is under you or not.

France. Since 2020, a series of prefectoral decrees along the Mediterranean coast forbid anchoring on Posidonia meadows. The rules vary by département and by vessel length. Broadly:

  • Boats over 24 m are prohibited from anchoring on Posidonia across most of the Var and Alpes-Maritimes coastline, with mandatory use of designated zones (ZMEL) or authorised buoys.
  • Boats between roughly 20 and 24 m face similar restrictions in the busiest sectors, including the Baie de Pampelonne, the Lérins, and around Porquerolles.
  • Smaller pleasure craft are not exempt in principle. The general environmental code still protects the meadow, and rangers can and do fine skippers of 10 m boats caught with chain in the grass.

Fines start around 150 euros for a fixed penalty and can climb to 150,000 euros under the code de l'environnement for damage to a protected habitat. Real-world cases have landed in the 500 to 1,500 euro range for recreational skippers. For the broader national picture, see our overview of anchoring rules in France.

Spain and the Balearics. The Balearic decree of 2018 (updated since) protects Posidonia across the archipelago. Anchoring on the meadow is prohibited, and in high-traffic zones like Formentera's Ses Salines park, only designated buoys or clearly marked sand corridors are usable. Enforcement is done by Servei de Protecció d'Espècies, and fines can reach 100,000 euros. Mainland Catalonia and Murcia apply the general Ley de Costas plus regional marine reserve rules, which produce a similar patchwork.

Italy. No single national ban, but marine protected areas (Cinque Terre, Portofino, La Maddalena, Egadi, Tavolara, and dozens more) each have their own zoning. Zone A is off-limits, Zone B usually requires a buoy, Zone C allows anchoring on sand. Outside MPAs, the seagrass is technically protected under EU Habitats Directive rules, but ground-level enforcement is patchier than in France or Spain.

Croatia, Greece, Turkey. Posidonia is present and legally protected on paper under EU or national frameworks, but active enforcement against recreational anchoring is still rare outside specific parks. That does not make it ethical to trench a meadow in Kornati because nobody is watching.

Reading the seabed before you drop

The single most useful skill for Med anchoring today is telling sand from Posidonia from above. Three tools, used together:

  1. Colour. In clear water and good light, sand reads as bright turquoise or almost white. Posidonia reads as dark brown, olive, or nearly black. The transition is usually sharp. Rock is grey to black with a mottled texture. If in doubt, the darkest patch is almost always seagrass.
  2. Seabed charts. The Donia app, produced by Andromède Océanologie with backing from Med marine agencies, maps meadow extent along the French, Spanish and Italian coasts at a resolution useful for anchor planning. It is free, works offline once tiles are downloaded, and colour-codes seabed by habitat. Medtrix and the Balearic Posidonia Maps portal cover similar ground.
  3. Sun angle. Aim to arrive in a cove between roughly 10:00 and 15:00 local time with the sun behind you as you approach. Backlit water hides everything. Polarised sunglasses are not optional.

Send a crew member to the bow before you slow down, not after. By the time you are drifting head to wind at 0.5 knots it is too late to reposition without a windlass ballet. If you have a shallow-water forward scan sonar, it helps confirm sand under the keel, but do not trust it to distinguish grass from sand alone. It sees depth, not botany.

Where you can still drop the hook

The good news: the Med is not closed. Meadows typically grow between about 5 and 35 m depth, on soft substrate. That leaves several categories of anchorage that remain fully legal and often less crowded than they were five years ago, because the fleet now piles onto the buoy fields.

  • Sand corridors inside meadows. Most large coves have gaps: intermatte channels of clean sand between meadow patches, usually running perpendicular to the shore. These are visible on Donia and from the bow in good light. A well-set anchor in a 20 m wide sand corridor with short scope is completely legal, provided your swing circle stays on sand.
  • Deep sand and mud beyond 35 to 40 m. Below the photic zone the meadow stops. You need chain, patience, and confidence in your windlass, but coves with a steep bathymetric profile (parts of Corsica's west coast, the Calanques, north Sardinia) offer plenty of legal deep anchorages.
  • Shallow shelves inside 3 to 4 m. Meadows generally start at 5 m and deeper, so a boat drawing 1.6 m can often tuck inside the meadow's inshore edge on clean sand. Wind exposure is the trade-off.
  • Designated ZMEL and eco-mooring fields. Not free (typically 15 to 60 euros a night depending on size and location), but they solve the problem cleanly. Booking apps for the main French and Balearic fields fill fast in July and August, so reserve as early as you would a berth.
  • Anchorages outside MPAs on rock-and-sand mix. Rocky coves with sand patches at the head, common along the Esterel and parts of the Costa Brava, remain viable if you can set in the sand and keep the chain from sawing on rock.

If you find yourself repeatedly locked out of your usual spots, it is worth rethinking home base entirely. Our piece on alternatives to ports for mooring your boat looks at dry stack and swing moorings, and the guide to the most beautiful marinas in the Mediterranean flags several that now include Posidonia-compliant outer anchorages managed by the port authority.

Setting and monitoring in mixed seabed

Once you have identified a legal patch, the anchoring technique itself matters more than usual, because your margin for repositioning is small. A few practical points:

  • Drop short, then pay out. Let the anchor touch bottom before running out chain, so it lands in the sand you chose rather than being dragged into the meadow while it sinks.
  • Scope discipline. Standard 5:1 scope in a 20 m sand corridor at 8 m depth gives you a 40 m radius swing. Check your circle against the meadow edges on the chart plotter before you set back on the hook. If the circle crosses grass, either shorten scope (and accept the reduced holding) or move.
  • Set gently. A hard reverse pull on a poorly-placed anchor is exactly what tears out rhizomes. Set at idle first, confirm hold, then load up.
  • Watch the swing. Wind shifts in the Med (sea breeze reversal, thunderstorm outflow) will move you across your circle within minutes. Our guide on how to know if your boat is dragging anchor covers what to actually watch, because most chartplotter alarms fire far too late.

For skippers newer to Med conditions, the fundamentals in how to anchor your boat safely are worth a re-read before the first cruise of the season. The physics are the same everywhere, but the consequences of a sloppy set are higher when the wrong bit of seabed is a protected habitat.

Planning the season around the new rules

Realistically, the direction of travel is one-way. Expect more zones to become buoy-only, more patrols, and higher fines. The skippers who enjoy the Med most over the next five years will be the ones who plan seabed the way they plan weather: at the passage-planning stage, not on arrival. Build a shortlist of two or three legal anchorages per leg. Book buoy fields when the plan is fixed. Keep a log of coves that worked, with the exact sand corridor coordinates, because you will want them next year.

This is where continuous position logging becomes genuinely useful. The Oria Box records every anchorage you visit, the swing pattern of your boat once set, and the exact track you followed in. If a cove worked, you have the data to return to the same 5 m circle of sand next season. If it did not, you know exactly where the meadow started. Which raises a question worth asking before you next drop the hook: do you actually know what was under your chain last summer, or are you about to find out the expensive way?