In baseball, a submarine is a pitch delivered with a three-quarter sidearm or underhand motion. The pitcher delivers the ball while almost scraping his knuckles on the dirt. The pitch has a tendency to break more than one delivered with an overhand motion. These are the toughest pitchers for right-handed hitters to hit off of (if the pitcher is right handed). But a lot of their breaking balls seem to float to a lefty. Pitches thrown via a submarine motion are also generally more difficult for hitters to see relative to pitches thrown via an overhand motion.

The rarity of submarine pitchers is sometimes attributed to the different technique required, rather than being an inferior pitching style. The technique is unknown to most coaches simply because the vast majority of pitchers use overarm motions. Thus, most young baseball pitchers are encouraged to throw overhand.

There are not many hard-throwing ones. Perhaps the most notable hard throwing submariner was Carl Mays, whose unorthodox delivery possibly contributed to the fatal beaning of Ray Chapman.

In the present day, Chad Bradford (Athletics), Jeff Nelson (Mariners) and Byung-Hyun Kim (Rockies) are regular submariner pitchers in the major leagues. Some in the past have been more deliberate, like Ted Abernathy, Kent Tekulve and Dan Quisenberry.