To prevent propulsion devices from colliding with each other by absorbing dislocation in parallel movement, in two water jet propulsion devices jointed for the parallel movement.

A water jet propulsion device obtains propulsion force by jetting sucked water from an injection nozzle 2. Adjacent steering nozzles 10, 11 of two propulsion devices are connected with an air-cylinder-shaped link 22. The respective steering nozzles reciprocate in the same direction by hydraulic cylinders 13, 14, and 15, 16. Ports corresponding to each set of the hydraulic cylinders are connected to each other through safety valves 50, 51. At the time of reciprocation, if parallel condition of the steering nozzles 10, 11 is broken, the piston 27 of the link 22 moves, and air in the air cylinder and a cushioning material function as dampers. In such a case as one of the hydraulic pumps is stopped, large operational dislocation is generated between the steering nozzles 10, 11. The link 22 ensures a minimum distance between the steering nozzles 10, 11, and avoids a collision. Excessive pressure generated in the hydraulic piping of a failed hydraulic system is released from the safety valves 50, 51.