The waters off France are paved with the wreckage of the Second World War. From the U-boats that prowled out of the Biscay bases, to the landing craft and blockships sunk off Normandy, to the scuttled hulks of the Mediterranean campaign, the seabed holds a war that ended eighty years ago and is still down there in the dark. For the cruising sailor who dives, this is some of the most sobering and rewarding underwater ground in Europe. It also comes wrapped in rules, because most of these wrecks are war graves.
I am a recreational diver who cruises, not a technical wreck specialist, and what follows is written from that position: where the wrecks are, what state they are in, and how to behave around them without breaking the law or your own moral compass.
U-boats on the Biscay floor
The German submarines ran out of bases at Lorient, Saint-Nazaire, Brest, La Pallice and Bordeaux, and a number lie on the bottom within reach of those ports. The best-known dive is the U-171, lost on 1 July 1942 in the Bay of Biscay and sitting at an average depth of around 39 metres. In 1999 the French authorities formally classified the wreck as a military grave, which sets the tone for the whole category: you may look, you may not take, and you may not enter human remains.
The bases themselves are still standing, the vast concrete pens too strong to demolish. The submarine pens at Lorient and Saint-Nazaire are worth a visit from your berth, and seeing the bunkers above water gives the wrecks below an extra weight. Lorient's Keroman base alone had seven cells built to shelter up to thirteen submarines at once.
A wreck at 39 metres is deep recreational diving, beyond the range and gas planning of a casual holiday dive, and the Biscay water is rarely as clear or as calm as a Mediterranean postcard. Treat these as serious dives, with a local operator who knows the site, the tide and the legal position.
Normandy: the invasion seabed
The seabed off the D-Day beaches is a category of its own, a single enormous archaeological site. Beyond the Mulberry caissons that still break the surface off Arromanches lie scuttled blockships, sunk landing craft, tanks, lorries and the general debris of the largest seaborne assault in history. The artificial harbour off Arromanches alone was built using 18 deliberately sunk blockships, and the wider invasion zone holds far more.
All of it is protected. The French state maps and guards this ground as maritime heritage, and the whole area is studied as the underwater archaeology of the landings. If you are cruising the coast above it, my account of the D-Day beaches from the water covers the surface picture, the caissons, the marinas and the tides. The diving here is for organised, permitted operations, not for a sailor who fancies a poke around on the anchor.
The practical message for the cruiser is simpler than the diving rules: do not anchor where you might foul a wreck, and treat every wreck buoy as a genuine obstruction.
The Mediterranean campaign
The south coast has its own war wrecks, from the Allied landings of August 1944 and the long Mediterranean naval campaign. Off the Var and the Cote d'Azur lie sunk landing craft, aircraft and shipping, generally in clearer and warmer water than the Atlantic, which makes the south the more forgiving place to start if wreck diving is new to you. Depths vary enormously, from shallow wrecks inside recreational limits to deep ones well beyond them, so the rule is the same as anywhere: dive with a local centre that knows exactly what lies where.
If your cruise is heading that way, the anchoring rules on the Riviera are strict for reasons that have nothing to do with wrecks, mostly the protection of seagrass, so read up on the posidonia anchoring ban in France before you drop a hook anywhere along that coast. The seabed there is protected coming and going.
The law you cannot ignore
France takes war wrecks seriously, and so should you. The headline rules:
- Military wrecks are war graves. The U-171 classification of 1999 is the model. Removing anything, including loose artefacts on the seabed around the wreck, is theft and desecration.
- Many wrecks are formally protected archaeological sites with their own permitting regime. Diving some of them requires authorisation.
- Unexploded ordnance is a real hazard on invasion-era sites. Touch nothing that might be live.
- Anchoring on or near a known wreck can damage a protected site and foul your ground tackle on steel that will not let go.
The simplest safe policy is to dive these wrecks only through a registered French dive centre that holds whatever permissions apply, and to keep your own boat's anchor well clear of charted wreck symbols.
Reading a wreck before you dive it
Part of the pleasure, and the safety, is knowing what you are descending onto before you splash. I spend time with the wreck's history first: what ship or submarine it was, how it was lost, what condition the divers before me reported. A submarine like the U-171 lying at 39 metres in Biscay current behaves very differently from a shallow Mediterranean landing craft sitting upright in clear water. The first is a deep, dark, often silty dive with strict gas and time limits and a real risk of disorientation; the second can be an easy potter in good visibility.
Visibility on the Atlantic side is the great variable. Biscay and the Channel can serve up a few metres of green murk one day and a respectable ten or fifteen the next, and the tide drives it. The Mediterranean wrecks are usually the clearer dives, which is one more reason to cut your wreck teeth in the south before tackling the deep Atlantic sites. None of this is gospel for a particular day, so the local dive centre's judgement on the morning beats anything written in a book months earlier.
How to fit a wreck dive into a cruise
Wreck diving and cruising do not always sit easily together, because the good wrecks tend to be offshore and the weather windows for diving them are narrow. What works:
- Base yourself in a port near the wrecks for a few days rather than trying to dive on a passage day.
- Book through a local centre and let them run the dive from their own boat. They carry the gas, the permits and the local knowledge, and you avoid putting your cruising boat on a marginal anchorage over a wreck.
- Build in weather slack. A 39-metre Biscay dive needs settled conditions, and you may wait several days for them.
- Carry your own logbook and certification cards. French centres will want to see them before they put you on anything deep.
Carry a delayed surface marker buoy and a reliable torch even on the shallow Mediterranean wrecks, because steel structure swallows the light and a clean ascent matters more here than anywhere. There is something particular about diving a wreck and then sailing on over the same water that took it down. You surface, dry off, hoist sail, and the sea closes over a story it has been keeping for eighty years. Treat these wrecks as the graves and monuments they are, dive them through people who know the rules, and they will give you the most serious underwater days a French cruise can offer.
