you can keep a xerox copy of your passport, id, etc
with you if you're more comfortable, and leave the original onboard.
Norwegian Sea, Roatan/Belize, Apr 2004
RCCL Splendour of the Seas, Western Caribbean (Cozumel/Costa Maya), May 2007
Princess Diamond, Mexican Riviera (Puerto Vallarta/Mazatlan/Cabo San Lucas), Sep 2006
Carnival Paradise, Catalina Island/Ensenada BC, Jun 2011