I can tell you as a photographer, any time you buy a waterproof case, no matter how much you spend and where it comes from, test it first. Learn the quirks about the opening/closing. I know that should be a given, but people overlook it. easiest check is get some colored construction paper, place it into the sealed case and dunk it into the bathtub, sink, pool, bucket. Something a little deep. if holds up, then take it to the pool bottom and let it float to the top.
Dry it off completely, as with your hands. Open and inspect.