Unknown waters: anchoring and speed done right

Five knots, seagrass, local decrees: how a captain checks anchoring and speed rules before entering waters they don't know.

9 June 2026 · 4 min read

Every captain knows the moment. The vessel is closing on a bay it has never visited, the day’s programme calls for a stop, and two questions surface at once: how fast may I approach the shore, and where am I allowed to drop the anchor? In yachting, where navigation is overwhelmingly coastal and stops follow the owner’s mood, these questions come up daily. The easy answer — “five knots inside three hundred metres” — no longer covers it. In the Mediterranean especially, local rules have multiplied and tightened, and improvisation now carries a heavy price.

Three layers of rules, stacked

To find your way, you have to see maritime regulation as three stacked levels. The first is international: the COLREGs, the rules for preventing collisions at sea, apply everywhere and at all times — the captain’s common foundation. The second is national: each state sets general rules — in France, the well-known 300-metre coastal band. The third, and the most treacherous, is local: maritime prefectural orders, municipal by-laws, marine-park and protected-area regulations. It is this last level that changes from one bay to the next, shifts every season, and is precisely what you don’t know when you discover a zone. The golden rule: local always overrides general, and local is what you must go looking for.

Speed: the 300-metre band and its overlays

In France, speed is limited to 5 knots within the 300-metre band measured from the shoreline — a general, permanent limit that applies even with no buoyage at all, and that also runs around islands, islets and drying rocks. Beware: the shoreline shifts with the tide, so on a big coefficient your 300-metre band moves with it. The maritime prefect can tighten the rules in defined zones — channels, swimming areas, reserves — and port entrances usually impose their own limits. Competence is split: the maritime prefect governs the navigation and anchoring of vessels, the mayor the activities run from the beach. The penalty is anything but symbolic: up to six months’ imprisonment and a €3,750 fine for a simple coastal speeding offence.

Anchoring: the end of improvisation in the Med

It is on anchoring that the landscape has changed most. To protect the Posidonia seagrass meadow — an ecosystem that grows back only centimetres a year — the Mediterranean maritime prefecture has built, on the back of its 2019 framework order, a web of decrees banning vessels of 24 metres and over from anchoring over the meadows. In practice, a large yacht must now either stay clear of the seagrass or use an organised anchoring zone or an authorised buoy field; even dynamic positioning is regulated. Penalties reach €150,000, alongside prison sentences and bans from navigating in French waters. The neighbours apply the same logic: in the Balearics, Decree 25/2018 bans anchoring on the “red” and “yellow” Posidonia zones, with fines that can climb to two million euros and a dedicated surveillance fleet through the summer; in Italy, the port authorities’ ordinances set the bans locally. Everywhere, the reflex is the same: you no longer anchor “by eye.”

The captain’s method: inform yourself before you anchor

The good news is that all of this information is public and accessible — provided you go and get it before you arrive, not once the anchor is on the bottom. These are the channels to cross-check, every time:

SourceWhat it gives you
Charts and Sailing Directions (SHOM / Admiralty)Seabed nature, regulated zones, dangers
Weekly Notices to MarinersFree chart corrections, published online
Urgent Notices to Mariners (AVURNAV)Wrecks, works, closed zones (VHF 16, NAVTEX, prefecture sites)
Maritime prefecture websitesOrders in force, by zone, downloadable
DONIA appPrecise seabed mapping: green = seagrass, no anchoring
Harbour office / local agentToday’s rules, notices in force, available buoy fields

A few reflexes make the difference. Call the harbour office on VHF before you enter: it knows the day’s notices better than any chart. Check the maritime prefecture’s website on the morning of departure — an order may be brand new. Read the seabed on screen before you pay out chain: on DONIA, green means no. Over 24 metres, book an organised anchorage or an authorised mooring, and do it early in the season. Distrust “it was fine last year”: the rules have changed faster than the habits. And log, in writing, why you anchored where you did — under inspection, a documented decision protects you.

Informing yourself about an unknown zone is not administrative box-ticking: it is a professional skill in its own right, on a par with routeing or weather. The captain who cross-checks the sources before easing off the throttle or dropping the hook turns a zone of uncertainty into controlled navigation — and shields the owner from the fine, the detention and the file that ends up before a judge. It is precisely this regulatory watch, kept up from ashore and constantly refreshed, that separates a serene operation from an exposed one.

By

Jean Pousthomis

Master Mariner · STCW II/2 unlimited · Founder & DPA, Cursorio

Master Mariner and founder of Cursorio. Externalised DPA for private superyachts held directly or via family office.

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anchoring coastal navigation posidonia regulation captain

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