To make a film arbitrarily producible of bubbles with fishes left as temporarily gathered, by making an underwater sailing body sail a programmable sailing route in the water, housing a gas accumulating storage vessel and chemically gas generating gas generator for generating a bubble in the underwater sailing body, and releasing gas during sailing.

An underwater sailing body main unit 12 is formed by a sealed pressure resisting can unit, and in an external wall surface thereof, bubble release holes 2 are formed as an aggregation of small holes releasing gas in the water from a gas chamber 16 in the inside filled with the gas. Compressed gas is supplied to the gas chamber 16 through a solenoid valve 5 from an accumulating chamber 6 with the compressed gas left as accumulated. A rudder 3 for making an underwater sailing body 1 sail by itself as programmed and a propeller 4 for propulsion in the water to be rotated by a motor 10 with a battery 8 serving as a power source are provided in the main unit 12. A screen of bubbles is formed by rising of the innumerable fine bubbles released from the bubble release holes 2 during sailing of the underwater sailing body 1, so as to leave fishes as temporarily gathered.