USS Mackerel (SST-1)
 SST-1 redirects here. For the experimental device see SST-1 (tokamak).USS Mackerel (SST-1) originally known as USS T-1 (SST-1) was the lead ship of the T-1-class of training submarines. She was the second submarine of the United States Navy named for the mackerel a common food and sport fish and was in service from 1953 to 1973. She was one of the smallest operational submarines ever built for the U.S. Navy.