Let's talk about the ATM, which generally described as '30 meters deep', while its actually means the pressure ratings not the depth rating. 3 ATM means that it can withstand hand washing while 5 ATM means that you can showering and dipping yourself in a pool. read more
Luxury watches are only waterproof to 3 atm (30m) because the people who make them believe that the customers don't get exposed to mega-sweaty situations. But consider this: some Australian celebrity emerges from their house in some snazzy suit, walks up some long and steep driveway and hops into the air-conditioned limo. read more
As Matt Saunders notes, "ATM" is short for atmospheres, and indicates the depth to which a watch is safe. 1 ATM means basically sea level, so 10 ATM means that the watch can withstand 10 times the pressure at sea level without allowing water into the watch. read more
Here's a short rundown of ATM ratings and how they pertain to how you can use your watch: 3 ATM: 30 meters/100 feet = Everyday use (washing hands, rain, etc). No swimming. read more