1. A triggering unit mounted in association with an elongated missile for slowing the travel of the missile when fired through a fluid medium which comprises: a. a member mounted to slide along the length of said missile from a first to a second position, b. braking means carried by said missile and controlled by said member, said braking means being disabled when said member is in said first position and being actuated into braking operation when said member is in said second position, means for maintaining said braking means positioned between opposite ends of said missile in both the disabled and actuated conditions, said braking means when in actuated condition extending out from the exterior of the body of said missile and transverse to the long axis of the missile to slow missile travel, c. means for urging said member from said first position to said second position, d. and means for controlling the sliding movement of said member from said first position to said second position to occur over a predetermined time interval, whereby said braking means is actuated at a predetermined time after said missile is fired, e. wherein said member includes a rod having four portions, the first portion being attached to a primary release means, the second portion carrying a pair of jaws having flanges thereon for engaging a slot in the missile housing, the third portion carrying the braking means and the fourth portion being attached to a spring which assists the sliding movement of the member, said flanges of said jaws when engaged in the slot of the missile housing will hold said spring in a compressed state.