The water-resistance of IWC watches is stated in bar and not in metres. Metres, which are often used elsewhere in the watch industry to indicate water-resistance, cannot be equated with the dive depth because of the test procedures that are frequently used. The following are some examples for explanation: an IWC watch with an indicated water-resistance of 1 bar is protected against splashing water. With water-resistance of 3 to 5 bar, the watch can be worn when swimming or skiing, and at 6 to 12 bar it will have no problem with water sports or snorkeling. Diver’s watches with an indicated water-resistance as of 12 bar are professional measuring instruments designed for scuba-diving. Special diver’s watches resistant to 100 bar or 200 bar are suitable even for deep-sea diving.
For a more detailed explanation, see here.