A water gun (1) has a casing (10), a rear grip portion (12) and a front grip portion (11). The casing (10) incorporates a pump mechanism (40) and includes pumping tubing (50) which makes up a pumping path through which water is pumped up from a water storage tank by the pumping mechanism and a muzzle portion (4) which is disposed at a front end of the casing (10). The pump mechanism (40) is made up of a first cylinder (20) and a second cylinder (30) which are oriented in opposite directions to each other and includes a first piston (21) slidable forwards and backwards within the first cylinder (20) and a second piston (31) slidable forwards and backwards within the second cylinder (30), an interlocking member that is coupled to the first piston (21) and the second piston (31) and which is brought into engagement with a rear half portion of the casing, pumping check valves (41), a jet water flowing chamber (22) and a water supply path (52).