We like beaches, but don't like just sitting there. We do the 5k, swim, do Pelican Plunge, eat lunch and get ice cream, and then rent some kind of water sports equipment. (We did kayaks last time. DD wants to do something like that again.) We are pretty active people, and find enough exploring, swimming, and kayaking/biking/snorkeling to keep ourselves busy.
This year DH and DD are doing the Castaway Ray's activity at 11 AM, so we'll have that between the 5K and lunch to keep busy.
There's plenty to do on a relatively quiet ship, too, so don't hesitate to hang on the ship and check that out! Look at the Navigator the night before and make some choices.