The Seabees had a divers school of their own to qualify 2nd class divers. During WWII being a diver was not a "rate", it was a "qualification" that had four grades: Master, 1st Class, Salvage, and 2nd Class. CBs would put men in the water from the tropics to the Arctic circle. In the Aleutians CB 4 had divers doing salvage on the Russian freighter SS Turksib in 42 °F water. In the tropics Seabee divers would be sent close to an enemy airfield to retrieve a Japanese aircraft. The Seabees of the 27th CB alone, logged 2.550 diving hours with 1,345 classified as "extra hazardous". Seabee Underwater Demolition Teams were swimmers during WWII, but postwar transitioned to divers. Another historic note to the Seabees is that they had African American divers in the 34th CB. Those men fabricated their diving gear in the field using Navy Mk-III gas masks as taught at diving school. Twice, while at Milne Bay, the 105th CB sent special diving details on undisclosed missions. At Pearl Harbor Seabee Divers were involved in the salvage of many of the ships hit on 7 December as well as the recovery of bodies for a long time after the attack. Their primary diving gear was modified Navy Mark III and Navy Mark IV gas masks.