I don’t think so...
Territorial sea, as defined by the 1982 United Nations Convention on the Law of the Sea, is a belt of coastal waters extending at most 12 nautical miles (22 km; 14 mi) from the baseline (usually the mean low-water mark) of a coastal state.
Cruise ships tied to the dock are subject to local, state and federal law until they reach international waters. The passport checks at the beginning are for confirming you can get back into the states legally (whatever “legal” means nowadays...)
I agree. And once beyond the limits the FBI still has jurisdiction over crimes involving US citizens.