<http://www.gwpda.org/photos/greatwar.htm#TOP>.
None the less, Submarines were still some of the most
feared weapons used during the war. It was one thing to fight in
a trench, or sail on a warship, where you knew an attack could happen
at any time. The German campaign for unrestricted submarine
warfare made almost anything afloat a target. Merchant ships were
sunk, and the sinking of the Lusitania proved how voracious the Germans
would be with their undersea weapons.
The success of the submarine was due to the way it
attacked. Submarines could hover just below the surface, out of
sight, and raise the periscope, point the sub at a ship, and fire a
torpedo, and disappear back beneath the waves. The ship wouldn't
even have the chance to react (or have anything TO react to) until the
torpedo hit. Once the submarine submerged, it was extremely hard
to find beneath the waves.
During World War One, there were 375 U-Boats built for the
German navy, and 6,596 ships were sunk by U-Boats over the course of
the war.
Even with these numbers, U-Boats were not impossible to sink.
The primary weapon used to sink a submarine was the depth
charge. Depth charges were large canisters filled with explosives
that were set to sink behind a ship, and detonate once they reached a
certain depth. When a submarine was spotted, depth charges would
be set for variable depths, and dropped into a warships wake.
(Think of them as giant underwater grenades). Depth charges
worked quite well, but it became almost a game to guess the depth of
the submarine, and there was a limited number of depth charges that a
given ship could carry.
Sometimes submarines would be blown up with the deck guns
of a warship, should the submarine happen to be caught while on the
surface taking on air and charging the batteries. Daring ship
captains also could simply run right over a submarine. The thick
hull of a warship was no match for the think skin on a submarine.
To keep the English Channel clear, a very simple age-old
device was used : the net. Nets were hung just below the bottom
of a normal warship in the water. And submarines would get
tangled in the nets below the water, and would be spotted if they rose
closer to the surface to try and go over the nets.