wetsuit, keycord / pocket compartment.
boardies in durban, used to have it in my pocket attached to that little cord, careful though as got eaten up once at cave rock and somehow decided to rip my pocket / key etc...surf was good so worried about it after i got out
never leave it anywhere near or in your car unlocked think its a stupid idea personally.
if you in durban either put a key ring through the leash plug rope if you think its strong enough and dont have issues with that and clip it on.
the other main thing i do in warmer water if possible use shoe laces for fin saves, thread it through the shoelace and tie a double knot. if good shoelace knot will never come undone only when you untie it and should never snap either.
if you goto more deserted beaches, take a towel and thread it through the corner of the towel and stash the towel but somewhere you can check from the water. owes arent really phased about scoping towels only and you have time if you see someone going for your towel as they still have to find the car etc
