I believe things have changed since the Clinton administration. I think U.S. sailors figured out then that the rules were not against travel, but were a trade
embargo, and sailors could at least reasonably claim they didn't spend anything while in Cuba. I understand Clinton was okay with this as it helped open realtions for a time, when the embargo might be lifted, yet technically, the embargo was still in place. However, I believe Bush changed that to a travel restriction based on national security
arguments so the restricitons are now what Dave M posted above. They are no longer based primarily on the long standing trade
embargo, but rather, actual travel.