I have a seven-year-old year old timex "diver" I've been wearing all summer. I often go back to this watch after I've sold off everything.
It is a snap-back, rated at 30m and I decided to take it in the water. I went off diving boards, executing thunderous can openers and Hawaiians, back-smackers, dove down to 13 feet, swam laps etc. The whole time the watch seemed fine.
Later that day I noticed condensation under the crystal. Yesterday I opened it up. Let me tell you, that snap back was near-impossible to get off. Inside the watch there was no sign of moisture, except what was observed under the crystal. I blew a hair dryer for a bit, dried it out and closed it back up --- Going with the brute-force approach, I covered the watch with a cloth and then used channel-lock pliers to snap caseback on. This didn't work too well, note the cracked crystal! The caseback is no longer flush, so this watch has seen its last water action.
However, if you consider the age of this watch, the snap back construction, the relatively-wimpy caseback gasket, the click-crown, the long term abuse, then you observe how it did in the water, you might conclude that your 200m or even 100m rated Casio or Seiko or Citizen would be just fine in the water.
Interesting facts about this watch:
-- it has smashed to the pavement several times in its life
-- it is running on the original battery
-- the dial still lumes decently, as does the minute hand. hour hand fades
-- the bezel does not turn
-- the caseback gasket is "integrated" into the groove of the caseback. I find this a nice feature since the gasket stays put when you remove the caseback, unlike the normal G-Shock O-ring, which invariably pops out, stretches, and is impossible to get back in place
-- I paid $49 for this watch direct from timex
-- the strap is an original Seiko Z-22 from my 7002 diver, bought new in 1991, sold (twice). I cut notches in the 22mm strap to make it fit the 20mm lugs
cheers
