Why don't you just Google "World War 1 Submarines?"
Submarines were sometimes referred to as submersibles.
1, 200,000 Soldiers 30 Warships 11 Submarines.
Atlantic Ocean.
Steel plates.
2,200,000 Soldiers 97 Warships 40 Submarines.
Yes, German submarines were very effective in both world wars. The Germans built excellent submarines and still do.
The US helped France in world war 1 with submarines in the Atlantic.
Yes, many submarines were used in WW1 by most of the major combatants.
World War 1
U-boats=Submarines
The Germans were the first to use Submarines in World War 1. Now i believe that the marines now do at times.