Swedish television just aired a documentary about a cave diving project, “Bjurälven”, in the north of Sweden. Due to extremely high water flows, the cave is only accessible for divers in the winter time. Which in northern Sweden can be quite cold. As you can imagine, this makes exploration of the cave quite difficult. As an example, the team has developed special heaters just to keep the regulators from freezing up.
More information on Expedition Bjurälven can be found here.