There's a similar law, the Jones Act, which passed early in this century, that offers protection for U.S. flag ships that carry cargo. Like most protectionist legislation, these were designed to save U.S. jobs and to protect the economic interests of ship owners and builders. The laws probably do help a bit. In the cruise business, for example, with the exception of one ship working the Hawaiian Islands, there are no large U.S. cruise ships afloat. There are a number of smaller passenger vessels on inland rivers or along the U.S. coastline but no big ones.
Cruise ships are notoriously closed-mouth about employee wages and working hours.
But those who go to bat for these workers, like the Center for Seafarers' Rights, paint the following picture. While officers who command the ship are often from Western Europe, the people who actually get their hands dirty are most often from Third World countries or Eastern European ones like Romania or the former Yugoslavia. They might get as little as two days off a month, and work six to 10 months before getting a larger bloc of time off. And all get free room and board, even if that might mean sleeping four to a small cabin. Yet these jobs are highly sought after.