Cruise.com via ShermansCruise offers a Carnival Cruise 5-Night West Caribbean Cruise for two, with prices starting at $518. (On the ShermansCruise landing page, scroll to the bottom and click "Book Now" next to the December 1 sailing date.) That's the lowest price we could find by $20. This roundtrip cruise aboard the Carnival Fantasy departs from Mobile, AL, on December 1. Book this travel deal by August 31.