No, no panic attacks. You get the standard navy medical screening, plus when you volunteer for submarines they ask if your claustrophobic. Other than that nothing special. Majority of the screening is informal, and done by the crew. Submariners are a pretty crust bunch, and have a tendency to “eat our own”. When you report to a sub as a brand new nub (non-useful body) you begin a year long process of proving to everyone on board that you have the knowledge and emotional toughness required to work in that environment. If you can’t, you are asked to leave (reassigned, usually after some disciplinary counseling). It’s not always a pleasant experience, by design. Your shipmates want to see what your limits are, since if you will crack under some “light” abuse, how are you going to cope with a real emergency? Not everyone handles this well, and some people leave. Like I said in another comment, they leave through suicide sometimes. Hopefully the Navy has gotten better about it, but in the 21 years I was AD, it didn’t change, and I don’t have much hope it has since then.