There are different answers to that but the most common one is that the USN had 288 submarines in WW2
326
2,200,000 Soldiers 97 Warships 40 Submarines.
The British lost 76 submarines during WWII.
1, 200,000 Soldiers 30 Warships 11 Submarines.
Yes, many submarines were used in WW1 by most of the major combatants.
Why don't you just Google "World War 1 Submarines?"
52
9
eighty five
759
USN about 250.
About 2,100 by many different countries.