A hydraulically actuated safety device has been built and has proved effective in reducing accidental, premature operation of oceanographic samplers. It consists of a cylinder, a piston, and a shear actuated by the piston. Increasing hydrostatic pressure acting on one side of the piston shears a pin at a predetermined depth, thus arming instruments sensitive to sudden motion.
Sachs, Peter L.. 1964. "A hydraulically actuated safety device." Journal of Marine Research 22, (1). https://elischolar.library.yale.edu/journal_of_marine_research/1021