Explorers off the coast of the UK have found 41 German and 3 English submarines from World War I.
"We divers only approach the boats with great caution. Venturing inside would definitely be extremely dangerous," Dunkley says.
It is hard to determine how almost a century of lying in place, as well as sedimentary deposits, have changed the structural integrity of the wrecks. If a U-boat turns over as a result of the divers' movements, its narrow corridors could become deathtraps.
The treatment of the crews' remains is also complicated. By law, the sites are considered inviolable gravesites. Nevertheless, the archeologists don't want to miss the opportunity to try to recover other signs of the erstwhile sailors in the underwater crypts. "Perhaps we'll find a cup or a sign with a name on it," Dunkley says.