Here is the story for high-end diver replicas ... they are great for water, but the quality control at the factory can be bad. If the guy in China who assembles your watch leaves out 1 gasket by accident, it does not matter if your watch is supposed to be waterproof.
If you pay for a good replica dive watch it CAN be waterproof; they are supposed to be waterproof .. but always check. It is not an expensive test, and the fix for a leaky watch is cheap too IF it is supposed to be waterproof.
I swim in the ocean, in pools, and shower will all my diver replicas .. no problem .. but never trust it until you check it.