How many submarines did we have in WW2?

We started with about 50 operational submarines. We built 221 and we lost 52. We ended the war with 179 boats in service with about 40 more in sea trials or still being completed. Definitions vary so it can be difficult to get consistent, definitive numbers.Contracts for many more of the Balao and Tench class boats were cancelled when it became apparent that they would not be needed for the war.

This refers only to operational boats. At the beginning of the war, we still had some old R-class boats and most of those were being used for training. Some S-class boats were being used for training while others were still operational boats at that time. (The R-boats go back to the early part of WW1 and the S-boats were built during and right after that war.) However, both classes had shorter range and many other limitations. The operational S-boats would become training boats as new construction could replace them.