Underwater kickoff device

The invention discloses an underwater kickoff device. During work, a heater heats a locking mechanism; the locking mechanism is made from a thermal cutoff, which breaks when heated; the device is located under water; a first segment of a sliding shaft is in contact with water; extruded downward by a force, the sliding shaft extrudes a second locking ball from a second through hole; a ball baffle and the second locking ball enter a cavity between a outer sleeve and a top cover; the sliding shaft slides downward in the inner cavity of a ball sleeve; when the first segment of the sliding shaft slides into a first through hole, a first locking ball doesn't extrude from the outer wall of the ball sleeve, because the diameter of the first segment is smaller than the inner diameter of the ball sleeve and the sum of the diameter of the first segment and two times of the diameter of the first locking ball is smaller than the inner diameter of a baffle ring; free from the lock and restraint of the first locking ball, t