What kind of training did they get for submarine duty?

Prior to the war, the usual program for diesel submariners was three months of sub school in New London for enlisted crew and six months for officers. This was in addition to any training for the enlisted crew in their ratings (specialties.) Once he got to his submarine, the training began in earnest.

During WW2, the training in sub school was condensed and sometimes skipped completely. If a sailor went to sub school at all, it would be about half the normal time or about six weeks for enlisted men and three months for officers. For experienced sailors, sub school may be skipped altogether.

NOTE: The process for submarine school has changed, particularly for those who have been nuclear trained. They will likely be sent directly to their boats after nuclear power school but without sub school. That way the nuclear power training doesn’t erode before they can use it.

When the sailor got to his submarine, it was assumed that he actually knew very little. In fact, that was correct in that he had little or no practical experience. His first job would be to become a qualified watchstander so he could start to carry his share of the workload. The next thing would be to earn his dolphins, to qualify for duty in submarines.

Qualifying usually required at least six months for enlisted men and at least a year for officers. He had to demonstrate knowledge of all the basic systems on the boat. For an enlisted sailor, this would mean passing an oral exam while going through the boat with the Chief of the Boat (COB) and then with the commanding officer or executive officer. An officer would qualify on another, similar submarine. That process would include a similar exam plus rigging the boat for dive, diving the boat and conducting a practice attack.

The key thing about submarines was that everyone needed to be able to respond quickly to any emergency. There were no damage control parties on a boat. It was up to whoever was in the space to respond and resolve an emergency. In order to do that, everyone needed to know the systems in any space.