I hate camps that don't allow sandals (Crocs I understand, they don't have good traction, but a full-foot sport sandal is another animal entirely.)
When we run into this, what DS wears is amphibious sneakers. The Land's End Trekker versions are a decent affordable one. Whatever you get, just be sure to let them dry in the sun at the end of every day -- they can get VERY smelly if you let them stay wet for extended periods of time.