PURPOSE: To activate water in a levee by permeating water rich in dissolved oxygen into the levee by a method in which a wave-breaking and stopping levee is provided on the land side of an underwater levee made of a porous material, a wave-breaking levee is provided on the sea side, and a wave-breaking trap is provided between the wave-breaking and stopping levee and the wave-breaking levee.

CONSTITUTION: In a breakwater for clarifying water to prevent the sea or lake from pollution, a base levee made of a slightly coarse porous material M is provided on the seabed ground, a wave-breaking levee (c) made of a porous material N suitable for the purpose is provided on the land side of the base levee, and a wave-breaking levee (a) is provided on a level of the surface of the sea on the sea side of the base levee. Then, a wave-breaking trap (b) is provided between the wave-breaking levee (c) and the wave-breaking levee (a) in such a way as to permeate the wave-broken sea water into the levee.