Dive watches are distinguishable by their high-water resistance and bulky appearance. They generally feature at least 100-200 meters of water resistance (the minimum recommended for scuba diving) but can be rated as high as 1000 meters. All dive watches have a rotating bezel for the purpose of timing dives. Other common features include screw down crowns and helium release valves to prevent damage caused by helium gas buildup. Dive watches offer a strong wrist presence thanks to their thick cases (usually housing automatic movements), which range from 38mm to 44mm in diameter.