Cruise.com via ShermansCruise offers a Carnival Cruises 4-Night Mexico Cruise for Two with prices starting from $408. (On the ShermansCruise landing page, scroll down and click "Book Now" next to the December 2 sailing date.) That's the lowest price we could find for such a cruise by $10. This roundtrip cruise aboard the Carnival Imagination departs Long Beach, CA, on December 2. Additional fees may apply. Book this travel deal by August 31.