We've been on 2 cruises to the Caribbean, both in January. The first one (Cozumel, Cayman, Jamaica) was perfect...warm weather, water nice to swim in. The second one was just (un)luck of the draw. Water was ok, could have been warmer. We were on a different cruise line and our itinerary went to Belize, Roatan and Cozumel. It was in the 70s at Cozumel. Water was chilly. However, we're from Texas and that week it snowed and iced in Texas (this doesn't happen in the area where we live near Houston), so we were feeling the remains of the cold front. It didn't ruin our cruise, but warmer weather and sunshine would have been nicer.