In baseball, a submarine pitch is one in which the ball is released underhand, and often just above the ground, with the torso bent at a right angle and shoulders tilted so severely that they rotate around a nearly horizontal axis. (This is in stark contrast to an underhand pitch in softball in which the torso remains upright, the shoulders are level, and the hips do not rotate.)
The "upside down" release of the submariner causes balls to move differently from pitches generated by other arm slots. Gravity plays a significant role, for the submariner’s ball must be thrown considerably above the strike zone, after which it drops rapidly back through. The sinking motion of the submariner’s fastball is enhanced by forward rotation, in contradistinction to the overhand pitcher’s hopping backspin.
Submarine pitches are often the toughest for same-side batters to hit (i.e., a right-handed submarine pitcher is the more difficult for a right-handed batter to hit, and likewise for left-handed pitchers and batters). This is because the submariner's spin is not perfectly level; the ball rotates forward and toward the pitching arm side, jamming same-sided hitters at the last moment, even as the ball drops rapidly through the zone.
The rarity of submarine pitchers is almost certainly attributable to its unusual technique. It is not typically a natural style of throwing—it is often a learned style—and because the vast majority of pitchers use an overarm motion, most young pitchers are encouraged to throw overhand.
Though the bending motion required to pitch effectively as a submariner means that submariners may be more at risk of developing back problems, it is commonly thought that the submarine motion is less injurious to the elbow and shoulder.
Past major league submariners include Carl Mays (whose unorthodox delivery possibly contributed to the fatal beaning of Ray Chapman), Ted Abernathy, Elden Auker, Chad Bradford, Mark Eichhorn, Gene Garber, Kent Tekulve and Dan Quisenberry. Steve Olin was also a submarine pitcher.
Shunsuke Watanabe of the Lancaster Barnstormers is known as "Mr. Submarine" in Japan. Watanabe has an even lower release point than the typical submarine pitcher, dropping his pivot knee so low that it scrapes the ground. He now wears a pad under his uniform to avoid injuring his knee. His release is so low that his knuckles often become raw from their periodic drag on the ground.