We've sailed the Grand twice to the western Caribbean. Loved it both times. I doubrt Princess has a bad ship.
Swimming with the stingrays in Grand Cayman is a must.
We also swam with dolphins in Cozumel. It,too, was a blas, but the more I've read, the more I've begun to wonder if we should be encouraging the capture, training, and imprisonment of these intelligent mammals for uor own enjoyment. But they're there, so swim with them, enjoy it, and think about it afterward! The dolphin swim is in a wonderful state park that deserves a half-day by itself.