What do you mean when you say this is what we called a submarine?

This is as far as the technology could go in the early 1940s. However, these boats, and all others of that era, technically, were just submersibles. They were surface ships that could submerge for relatively brief periods (usually 16 hours or so), could fight submerged and then could come back to the surface. The first true submarine was the USS Nautilus (SSN-571) which was commissioned in 1954. With nuclear power she could operate underwater for a couple months at a time and did not have to surface regularly for fresh air or to recharge batteries. She was designed to operate underwater for the vast majority of the time.