For American submarines the relevant measurement units are yards, nautical miles and feet. The low depth meter stops at 165 feet, the higher depth meter shows deeper levels in feet. There are about 2,000 yards in a nautical mile, making calculations very easy.
The number of hundred yards you travel in three minutes is equal to your speed in knots by the way. That's how you measure target speeds. Time two positions 3 minutes apart, if they are 1100 yards apart the target is moving at 11 knots.
American subs must be fought differently than U-boats. They are much faster surfaced than the U-boats and that is the natural realm of the submarine, on the surface, scanning the most square miles of ocean in 24 hours, submerging only when necessary and then only for the minimum possible amount of time. On the huge Pacific hunting is a numbers game. Your number of targets will always be proportional to the number of square miles of surface you can search in a day. A submerged submarine is harmless to the enemy and a danger to itself. The mission of the submarine is to be dangerous, and a submarine hiding at 400 meters is completely safe to the enemy. Don't let them be safe.
The best remedy for being in fear for your own life is to make the enemy more afraid for his. Quit hiding and attack!
Your next obstacle is going to be "The American TDC is just CRAZY!!!!!" It is very different. But it is different with a stroke of genius. Everything the German TDC can do, the American can do. But the opposite is not true. There are special capabilities there which are well worth learning. I've made a practice of teaching German techniques adapted for American submarines with the Dick O'Kane and John P Cromwell manual attack methods. It works great. But you cannot adapt American targeting procedures to U-boats. They didn't have the tools to do that.