PURPOSE: To reduce oscillation and to activate the underwater creature atmosphere by providing a waterborne floating structure or a building and a fish reef having a braid-like, cage-like or frame-like structure and attached to the waterborne floating structure in the part of the structure or the building which is submerged in the seawater.

CONSTITUTION: A fish reef 30 is provided to a waterborne floating structure 10 including a pontoon 11, a house boat floating house or shop 12 and the like in the port which is submerged in seawater. Since the fish reef 30 which is braid-like, cage-like or frame-like is provided in the part of the waterborne floating structure which is submerged in seawater, the fish reef has a role of an oscillation restraint (as a stabilizer) in addition to the role of the fish reef. Further, if octopus pots are attached to the fish reef, octopuses who eat shellfishes or the like live therein so that coating of paint which is possibly toxic is unnecessary.