Rare Hedgehog projector at the USS Silversides museum.

 Hedgehog weapons, Mark 10 and Mark 11, were ahead-throwing weapon projectors. The weapons were adapted from the British. Fired from a steel cradle, six rows of spigots fired 24 projectiles. The projectiles were 7.2 inches in diameter and weighed 65 pounds with an explosive charge of 35 pounds. The advantage of the Hedgehog: they only exploded if they hit something; if unsuccessful, the attacks did not disturb the water for sonar performance; and the projectiles had a higher sink rate than convential depth-charges. The only disadvantage was that it could not be used on smaller patrol craft, which led to the development of the Mousetrap weapon.