As Elaine said, the water clarity should make debris easy to see but if you are concerned I would suggest something more substantial such as a water sandal with a more rigid sole. In the past I have seen some pretty nasty nails and metal after hurricanes. It is usually exposed and easy to see but if one did step on it there could be some major injury. Anything you choose to wear in the water will also capture a lot of sand that will continue to come out of the shoe, sock or sandal once you are out of the water.