The invention relates to the field of buoyant bodies, and more particularly to an annular buoyant body (1) including a central moonpool (2), configured such that, in water, with swell of a period substantially equal to a natural period of the buoyant body (1) while it is moving with heave motion, vertical forces exerted on the buoyant body (1) by a mass of water oscillating in the central moonpool (2) in phase opposition relative to the swell, compensate at least partially for the vertical excitation forces exerted on the buoyant body (1) by the swell. The invention also relates to a method of at least partially extinguishing heave motion of the buoyant body (1) at a natural period of the buoyant body (1).
