Anchoring in the Balearics: posidonia rules for sailors

In the Balearics you may not drop your anchor on posidonia seagrass. That is the core rule for every charter crew in Mallorca, Menorca, Ibiza and Formentera: anchor on sand, pick up a buoy in a regulated buoy field, or go into a harbour. The Balearic government publishes maps and web tools that show where the meadows are, runs bookable eco buoy fields in summer, and sends patrol boats that will ask you to move. This guide explains the rules and how to follow them without spoiling your week.

Why posidonia matters

Posidonia oceanica is not seaweed but a flowering plant found only in the Mediterranean. It grows very slowly, and the Balearic government lists what its meadows do: they fix CO2 and produce oxygen, protect sandy beaches against erosion, produce much of the sediment that becomes beach sand, and act as feeding ground and nursery for young fish. The Balearics hold about half of all posidonia recorded in Spain, and the meadows between Ibiza and Formentera were declared UNESCO World Heritage in 1999.

The problem for sailors is mechanical. The government's Natura 2000 description says an anchor tears off leaves and rhizomes and can rip out whole clumps, and a dragging chain does the same. Because posidonia grows so slowly, the damage lasts.

The rules for anchoring

Since March 2026, a national Spanish rule, Real Decreto 191/2026, also generally prohibits anchoring on posidonia and cymodocea seagrass meadows everywhere in Spain, including on nearby sand if your chain or swinging circle reaches the meadow, and over meadows only authorised buoys may be used. So the Balearic rules below now sit on top of a national ban.

The legal basis is Decree 25/2018 on the conservation of Posidonia oceanica in the Balearic Islands. For a charter skipper, the key points are:

• Anchoring on posidonia is prohibited as a general rule (article 7.1). This applies to all boats, whatever their size.
• The only way to lie over posidonia is on an authorised low-impact mooring, a single eco buoy or a buoy field (article 7.2).
• Inside a buoy field you must use a buoy, or anchor on the sand patches that belong to the field. You may never anchor directly on the meadow there.
• Your chain counts too. If there is posidonia close by, neither the chain nor any other part of your ground tackle may touch it (article 7.3). So anchoring on a small sand patch surrounded by seagrass is not enough if the chain swings over the meadow.
• Pumping bilges or dumping waste inside a buoy field counts as an aggravating circumstance (article 7.4).
• The only exceptions are force majeure and danger to life or to the safety of navigation (article 7.5).

Charter companies must brief renters on the posidonia ban and protected areas under the Balearic boat rental decree (Decree 44/2025), so listen at check-in.

How to recognise posidonia

The government describes meadows that usually start at about 3–5 metres depth and reach down to around 30–40 metres (deeper in very clear water). The leaves grow long and dense in spring, and in summer they turn whitish as organisms cover them. From the deck, meadows usually look like dark areas and sand like light, bright patches. That is a useful first check, but shadows, rocks and weed can fool you, so do not rely on your eyes alone.

The government's good-practice advice on Atlas Posidonia adds:

• Check the seabed with a seabed viewer (a glass-bottomed bucket) or your instruments, and use the government viewer to find the best spot.
• Work out where the anchor and chain will lie, taking into account boat length and the strength and direction of the wind. The bigger the boat and the stronger the wind, the more chain you need, and the further from the meadow you should drop.
• When weighing anchor, motor forward so the anchor lifts vertically instead of being dragged through the bottom.
• Pump bilges only in port facilities or at least 12 miles offshore, and take your rubbish back to port.

How to find a legal spot

Decree 25/2018 requires the posidonia maps to be made available to sailors and, where possible, to appear on nautical charts. In practice there are three tools.

• The government web app. The Balearic government's anchoring help app, ideib.caib.es/posidonia, shows the mapped meadows so you can check a bay before you drop the anchor.
• Phone apps. The government's posidonia cartography page also points to the apps Projecte Posidonia, Posidonia Maps and Donia (Android and iOS). The government reports that more and more sailors check them before anchoring.
• The Posidonia phone line. In season the government's posidonia service answers anchoring questions on +34 617 975 172 (check caib.es for current hours).

Eco buoy fields

Where a popular bay has seagrass, the answer is usually an eco buoy field. Ports IB, the Balearic ports authority, runs the regulated fields and takes bookings on its online reservation platform. The same platform also books transit berths in the harbours Ports IB manages directly. The fields include:

• Mallorca: Sant Elm, Cap Blanc–Cala Blava, Formentor
• Menorca: Badia de Fornells, Illa d'en Colom–Cala Tamarells
• Ibiza and Formentera: Platja de ses Salines, Badia de s'Alga–s'Espalmador, es Caló de s'Oli

The buoys are laid in summer, normally from 1 June to 30 September, and some fields have been kept open until mid-October. You can book a swim stop, a day or an overnight stay, and buoys are sized by boat length (8, 12, 15, 20 and 25 metre classes). Once you have an account you can extend, change or cancel a booking. In July and August, book as soon as you know your route, because the number of buoys in each field is limited.

Harbours

If a bay is all seagrass and the buoys are taken, go into a marina or harbour. It is the simplest legal option.

Cabrera and other special areas

Cabrera National Park

The Cabrera Archipelago Maritime-Terrestrial National Park, south of Mallorca, has its own permit system, run by the Balearic government. According to the official authorisation page, all applications are made online through the Cabrera reservation centre:

• Navigation permit: free and valid for 12 months. You need it just to sail inside the park.
• Overnight stay on a buoy: booked separately. Numbers are limited to 50 boats a day, and the maximum stay is two nights in July and August and seven nights in the rest of the year. Buoys are yours from 18:00 on the first day until 17:00 on the last day and are sized by boat length.
• Diving needs its own authorisation.

MITECO's visitor rules add that you go ashore by dinghy in Cabrera harbour (you may not moor at the main quay), that all recreational and spearfishing is banned in the park, and that there are no restaurants on the island.

Ses Salines Natural Park (Ibiza and Formentera)

About 85% of this park is sea, and its posidonia is the UNESCO-listed meadow. The park's page sets out the rules: anchoring only on sand, never on posidonia or in no-anchoring zones. Staying overnight at anchor is possible, but the park requires a permit (daily or annual) from the Balearic government. At s'Espalmador you may anchor only in the designated zones and land only through the marked entry and exit channels. Mud bathing in the lagoon is banned, and so are jet skis and spearfishing.

Natura 2000 bays

Around 75% of Balearic posidonia lies inside Natura 2000 sites, whose management plans regulate anchoring and apply where they are stricter than the decree. Check the chart and the government map in any protected bay.

Fines and enforcement

The Posidonia Surveillance Service, run by the Balearic nature institute IBANAT, patrols from mid-May to early October. It is at full strength from 1 June, working with environmental agents, Ports IB, the Guardia Civil and island councils. Its main job is to inform and help crews before they anchor and to move boats that are lying on seagrass. In one recent season it carried out more than 150,000 anchoring checks and moved over 10,000 boats. Environmental agents issued formal reports for illegal anchoring.

Under Decree 25/2018 (article 13), a breach is an administrative offence under Spain's Natural Heritage and Biodiversity Law (Law 42/2007) and the Balearic LECO law, and "alteration of the habitat by anchoring" is named explicitly. Under Law 42/2007, article 81, fines range from 100 to 3,000 euros for minor offences, 3,001 to 200,000 euros for serious ones and 200,001 to 2,000,000 euros for very serious ones. The penalty depends on factors such as the damage done, and for posidonia the decree says the area of meadow affected is taken into special account. Under the LECO law, the government's Atlas Posidonia gives 100 to 450,000 euros.

FAQ

Can I anchor on sand next to posidonia?

Yes, as long as your anchor lies on sand and neither the anchor nor the chain can reach the meadow as the boat swings. Allow for wind shifts and extra scope.

Do the posidonia rules apply to small boats and dinghies?

Yes. Decree 25/2018 bans anchoring on posidonia for all boats, whatever their size.

Do I have to book the eco buoys?

Yes. The Ports IB buoy fields are booked online through the Ports IB reservation platform, for a swim stop, a day or a night. Cabrera buoys are booked through the park's own reservation centre.

What happens if a patrol boat finds me on seagrass?

The surveillance crew will normally explain the problem and ask you to re-anchor on sand or move. Environmental agents can also file a report, which can lead to a fine.

Do I need a licence to skipper a charter yacht in the Balearics?

Yes, unless you hire a skipper. See our guide to the boat licence in Spain.

Planning your Balearic sailing week

Charter yachts are available from bases around Mallorca, for example Port de Pollença, and on Ibiza, bareboat or with a skipper. For more areas, see all boats in Spain. Then plan your route with our area guides: a sailing week from Palma to Cabrera, North Mallorca and Menorca and Ibiza and Formentera.