This may still apply
Ship and airline crews do not operate on work or tourist visas. They have specific crew visas
Essentiallly it means they must depart on the same vessel they arrived on. So a problem if you fly in as crew on your crew visa and then leave to say the Bahamas’s for a week (nearly had some mates deported from the US because of this)
For maritime there is a very strong chance these crew do not have visas of any sort, in which case they are prohibited from leaving the ship while it is in port. This means, unless they get dispensation, they cannot get off the ship and take a flight home.
At one point I had crew visa, work visa and tourist visa for the US. I became better versed in immigration law than most immigration officers. Learned this the hard way, checked into the USVI on my crew visa (was the captain of a charter yacht) then put the boat into a shipyard and was headed to Miami to pick up another yacht for delivery. The INS sure were not happy about me attempting to depart on a commercial flight as a passenger after entering on a crew visa. I kindly explained I could not solve the problem by departing on the yacht I arrived on as it was in the midst and f a tear down. But if he liked I could sneak out “illegally” and come back on a tourist visa if he really wanted. Somehow he saw sense and let me depart.