To prevent heat deformation, stress increase, and the like by supplying sea water of low temperature from one side wall of an internal partition chamber within a float and by discharging it from the other side wall thereof.

A float-type structural body 1 having a box-like structure floating on the surface 2 of the sea is comrised of a floating deck 11, front and rear end side walls 12, 13, light and left end side walls 14, 15 and a bottom 16 of a floating body. An internal wall 3 is positioned to be lower than the floating deck 11 by height (h), forming an internal partition chamber 4 between the decks 11. By forming the chamber 4 in floating-type construction 1, a pump 5 pumps up low temperature sea water from deep area, where is hardly susceptible of outside field, through a suction pipe 7, and the sea water is fed into the chamber 4 through a water feed pipe 8. The sea water is drained from a drain pipe to the outer field after cooling the floating deck and the like. Repeating such cycle, the temperature of the sea water contained within the chamber 4 is prevented from temperature increase even at the day time.