 All models feature 300-meter (1000 feet) water resistance.The Rolex Sea-Dweller, developed in 1967 but introduced to the general public in 1971, is a heavier-duty steel version of the Submariner, with a thicker case and crystal, as well as a date feature, sans cyclops magnifier.The Sea-Dweller incorporates a helium escape valve for use when decompressing and helium is in the gas mixture of a pressurized habitat; this model (ref 16600) has a guaranteed waterproof depth of .