The basic waterproof nature of any watch depends on it's design. Is it a replica of a waterproof watch, to begin with? For instance, a Daytona replica with screw down chrono pushers is theoretically far more waterproof than a replica of a non-divers watch, even tho it's a chronograph.
The bottom line, tho, is that any replica watch you buy will have almost no quality checks at the factory. The waterproofing gaskets could be completely missing from the watch you receive. No one checks.