General rule amongst actual divers
is that devices which are waterproof only as a secondary feature are only reliable up to about 10-20% of the stated depth. So a 200m normal watch might be useful for a normal 30m dive or might implode, while a 50m divers watch will probably work to 50m.
( Fronds are waving gently on, Fri 30 Sep 2011, 13:54, 1 reply)

Divers watches are the dog's because they're tested doing what they're designed for. Watches which say 200m would probably be ok sitting in a static tank at 200m equivalent, but when you're swimming about and knocking it off your diving tank the actual pressure your watch sees varies quite a bit. I've got a Tag which has 200m on it and I wouldn't take that deeper than snorkeling.
( AWPS, Fri 30 Sep 2011, 15:55, closed)

Mmm
I have a watch which is water resistant to 30m. Apparently, that translates to "Don't submerge it in water"

en.wikipedia.org/wiki/Water_Resistant_mark
( le brian, Sat 1 Oct 2011, 10:51, closed)