Usually they have a rubber bottom and a mesh uppers (or something that's like a wet suit material for uppers).
If you plan on wading out into the water in Serenity Bay (adult beach @ CC), water shoes ARE A MUST. Because this beach is open to the ocean (no protective nets, etc) there are sea urchins (sp?). It's not very plesent to step on one with bare feet (stinging spines break off in your foot and could cause walking difficulties for days).