Is water resistant the same as water proof ? If it isn't Whats the difference ?

Im asking this because the Casio website says some gshocks are water resistant. My friend (she has one) keeps telling me its water proof, and I keep telling her its not the same thing, but i want to make sure. And she's been bragging because I got a waterproof camera that goes 10ft underwater, and she says her gshock (200m) goes farther underwater without any harm done, and I dont believe its true because why would someone wear a watch 200m (365 or so feet) underwater, I dont even think anyone has been that deep, well unless theyre proffesional divers or something. Anyways yeah please help ?