Cruise.com via ShermansCruise offers a Carnival Cruises 4-Night Mexico Cruise for Two with prices starting from $398. (On the landing page, scroll to the bottom and click "Book Now" next to the December 3 sailing date.) That's tied with our mention from last week and the lowest price we could find for such a cruise in December by $40. This roundtrip cruise aboard the Carnival Imagination departs from Long Beach, CA, on December 3. Additional fees and taxes may apply. Book this travel deal by July 30.