Hmm I have never opened the water proof ones. The standard disposables lock together with plastic clips at the sides under the sticky labels though. I am not sure there is a way to reuse them, unless you unwind a whole roll and load that. Would seem pretty tricky, btw make sure the flash is discharged. that capacitor packs a mighty punch if you touch the circuit board.
There is a loop on the housing for the rubber band that is used as the camera strap. Right there where the front and back come together there is a slot in the plastic for a screwdriver blade. My daughter found the slot. Takes a pretty good twist.
I also took apart the main camera, which was probably sacrificial, but enlightening. It looks like it should be reloadable.