BRUSSELS (Reuters) - The well-preserved wreck of a World War One German submarine, possibly still containing the bodies of its 23 crew members, has been found off the Belgian coast. The use of submarines, often referred to as U-boats, in World War One to disrupt British trade routes in the English Channel and the North Sea was a key part of German tactics. The 93 German U-boats stationed in Belgian ports downed more than 2,500 ships but were also a target themselves, with 70 of them lost at sea, killing 1,200 sailors.  It was not yet clear which of the 11 known wrecks of the German submarines had been found, and authorities said they would not give the exact location of the wreck to deter looters.  Of the 11 downed U-Boats in Belgian waters, this one is the best preserved example,  the province of West Flanders said. Belgium s North Sea minister said he would investigate whether the wreck could be recognized as a heritage site. 