I found this story about the Royal Navy:

Prince William’s secret nuclear submarine mission

 

London, June 20 : Britain’s Prince William spent 24 hours under the sea on secret war games inside a nuclear submarine as part of his two-month attachment to the Royal Navy.
The young royal, who holds the honorary title of Commodore-in-Chief, Submarines, participated in an exercise to track down and destroy another sub.

As soon as he boarded HMS Talent, the T-Class hunter-killer immediately submerged off the coast of Plymouth.

He spent time in the control room, beside the nuclear reactor and in the torpedo room, which has cruise missiles.

And finally he was winched off the sub by a Sea King helicopter.

According to a Royal source, the prince was ‘fascinated’ by the experience.

“Prince William has huge respect for what submariners do and the sacrifices and discomfort they put up with,” The Sun quoted a source, as saying.

“He was very keen to see what their life was like,” the source added.

[1] http://www.newkerala.com/one.php?action=fullnews&id=75536