Watches for diving at extreme depths are available and they can be certified to more than 1,000m (3,281 ft). The diving depth record for off shore diving was achieved by a team of professional divers in 1988. They were performing pipe line connection exercises at a depth of 534 meters of seawater (MSW) (1752 ft) in the Mediterranean Sea. They were using watch for diving called were the Rolex Sea Dwellers that are the standard issue diving watch for every Comex diver since 1976.
In 1992 a Comex diver achieved a record of 701 MSW (2300 ft) not actual diving but in an on shore hyperbolic chamber. The watch for diving used during this scientific record dive, where a hydrogen-helium-oxygen gas mixture was used as breathing gas, was also a Rolex Sea Dweller what is ater resistance rating to 1220 meters (4000 ft). The high costs involved and the use of under water vehicles as reduced the need for watches for diving at extreme depth.
Some of the watches for diving extreme depths are filled with silicone oil exploiting the virtual incompressible of liquids. For example of diving watch by Sinn UX (EZM 2B) which case is certified for 12,000 meters, however, the quartz controlled movement can only withstand a depth of 5,000 meters. This technology only works with quartz movements as a mechanical movement does not work properly in the oil filled case. An advantage of this technology is that the time can be read very well under water.