Watch Water Resistancy Explained | Whats best for your purpose?

Water RatingDefinitionSuitable
IPX7With stands incidental exposure to water of up to 1 metre for up to 30 minutessplashes, rain or snow
IPX6Protected against powerful jets of water. Water projected at all angles through a 12.5 mm nozzle at a flow rate of 100 liters/min at a pressure of 100 kN/m2 for 3 minutes from a distance of 3 metresheavy spray, driving rain, boat washing, outdoor use in rough sea conditions
1ATMWith stands pressures equivalent to a depth of 10 metressplashes, rain or snow
3ATM 3barWith stands pressures equivalent to a depth of 30 metresSplash proof only, rain or snow, 
5ATM 5barWith stands pressures equivalent to a depth of 50 metressplashes, rain or snow, Pool swimming
10ATM 10barWith stands pressures equivalent to a depth of 100 metressplashes, rain or snow, swimming, diving into water, snorkeling
20ATM 20barWith stands pressures equivalent to a depth of 200 metres Scuba diving, snorkeling, and high-speed water sports
Christies Online does not recommend that any watch be used in hot water - Spa's, showers etc as the hot water expands the air inside the watch breaking the seals. The result is when the watch cools it can drag moisture back into the watch movement.