A definite pack item, I found the "ugly" black strap type sandals that resemble tires in my opinion work well too. Just make sure there is a back strap as flip flops come off.
I would go with the idea of the shoes perhaps making a one way trip--so much sand, and sometimes smell. Yes, there is definite coral and items to step on.
Don't forget boys dandals can fit girls and women for a cheaper price.
San Juan: Dorado beach: Embassy Suites Hotel beach: Gorgeous pool, extremely rocky and coral "man made cove area, not what I'd call a quality beach.
St. Thomas: Saphire beach--very nice, offered shade, some areas coral or rough ocean floor.
Antigua: Line? beach (across island from dock) nice sand, literally dropped off 50 feet from beach. No need for shoes.
St.Maarten: Orient beach---shoes needed for walk to beach, Atlantic side-waves etc, and optional clothing. Not the prettiest of the beaches we were at. We stayed at family end but some people still wandered "naked"