The Neptune (YDT-17), first of two 275-ton, 20-knot diving training tenders assigned to the Naval Diving and Salvage Training Center, Panama City, Florida, was completed on 25 February 1999. Her sister, the Poseidon (YDT-18), was planned to complete in May. The pair, ordered in June 1997 for $10.5 million from Swiftships, Inc., Morgan City, Louisiana, are to replace the World War II-vintage Phoebus (YDT-14, ex-YF-294) and Suitland (YDT-15, ex-YF336) and now are the only diving tenders on the Naval Vessel Register. The aluminum construction, 136-foot pair have a crew of eight and can carry seven instructors and 25 trainees. Twin 1,300-brake-horsepower Caterpillar diesels drive Hamilton waterjet propulsors, and the craft are rated capable of operating in up to sea state 4 and up to 200 nautical miles from land.