Do you need a license to operate a submarine?

Answer 1

For personal watercraft submarines (those that don't really dive but can go underwater a small amount) it depends on the locality, similar to any State, City, or Town that may or may not require a license to operate certain vehicles.

For larger submersibles (1 and 2 man submarines), they need to be fully certified and they're large enough to require a ship/tender to be launched from, so rather than a license, there's usually a certification/qualification procedure that the pilot must go through.

For tourist submarines, licensing is the same as it is for any maritime vessel carrying passengers.