Submarine training includes how long underwater?

Answer 1

All Submariners, regardless of rank, are always in some type of training, either underway or in port. There is no "training dive" if that's what you're referring to. All new crew members submerge with everyone else. I was asleep for my first submergence.

Submarine Sailors are trained at Submarine School in Groton on basic submarine operation, damage control techniques, history, and many other subjects pertaining to submarines as a weapons platform. No one who is assigned to any submarine is ever clueless - even in Submarine School you are tested to see if you can properly deal with pressure changes in a controlled pressure chamber. You are placed in a Damage Control trainer (known as the "Wet Trainer"), in which you're subjected to real-world flooding and damage conditions and expected to deal with them. You are given training on a Control Room simulator as well.

In other words, you're not thrown in blind. Everyone knows what to expect before they get there.