"In such a submarine there were, as standard, 22 crew members and a commander", West-Flemish Governor Carl Decaluwé said.
The UB II-type dive boat that was found is 27 meters (88 feet) long and 6 meters (almost 20 feet) wide, and is lying at about a 45 degree angle, between 25-30 meters (82-98 feet) below the surface.
Mr Decaluwé told reporters on Tuesday that the location of the wreck was being kept under wraps to prevent people going near it and to stop the submarine being looted or damaged.
The North Seas minister of Belgium told Reuters he would try to get the area designated as a heritage site.
Decaluwe said the U-boat was found by researchers.
German authorities could then check it against their record and contact the families of the deceased.
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A website, Uboat.net, tracks the submarines lost in both World War One and World War One, as well as casualties suffered by their staff.
An intact submarine dating from the First World War has been discovered at the bottom of the sea, just off the coast of Belgium. Using the submarines to disrupt British trade routes in the English Channel and the North Sea were a key tactics for the German military during World War I.
From the damage to the front of the vessel, it appears that the sub may have struck a mine with its upper deck.
Historic England revealed the images to mark the centenary of Germany's declaration of unrestricted submarine warfare on Britain.
Its base was in the medieval city of Bruges, 12 kilometres from the coast but linked to the sea at Ostend and Zeebrugge by canals.