I've reloaded single-use cameras for fun, but not something I'd do instead of a proper camera. Like others said, with slide film it would be more of a problem. With the prices of used equipment, you could probably pick up something decent at a garage sale or thrift store and not worry about it getting hurt.
If you are careful, there is no reason to not take your regular camera to the beach. I have seen some people basically put a camera in a bag, with the lens sticking out, to protect from sand, dust, and spray (though not much good if you drop it in the water).