If he has been selected for submarine duty he is going to one of two communities; Nuclear or Supply Corps. Even though he doesn't specifically come right out and say "I have been selected for sub Nuke.", I think it's a safe bet he is.
Having said that, I may be reading Already Gone's response wrong.
Obviously, you have to qualify for selection before they will send you there.
Some food for thought:
- With prior enlisted service, specifically a minimum of 4 years, you should be getting commissioned as an O-1E, not a regular O-1. Difference in pay. If unsure, ask NOW, and keep asking until you are shown, in writing, that you are not in that category.
- The biggest challenge I saw people face is that the Navy has one way of teaching things in the pipeline. Go with it. Don't think you know a better, faster, super awesome, etc. way of doing the things that will be presented to you. Part of the pipeline is about achieving and maintining uniformity. Everyone learned everything the same way, thinks the same when it comes to solving plant related questions, does the math the same way, etc. Failure to adapt, be assimilated

, will severely hinder your potential success.
- Listen to your Chief. Your sailors are your number one assest, treat them that way and they will bend over backwards to take care of you as well.
Best of luck and thank you for continuing to serve!