PURPOSE: To eliminate interference between audio equipments while by no means disturbing the flow of water along the bottom of a ship, by arranging the shape of cross section of the ship bottom to form several stages on different levels in symmetry between right and left sides almost along the hull with the center line thereof as the lowest stage.

CONSTITUTION: The low-stage ship's bottom 1a is set at the lowest position on the center line CL of the hull 2 while a dome A is projected downward toward the bow on the low stage ship bottom 1a. A middle-stage ship bottom 1b is provided in a pair, one on the right and the other on the left, on different levels marginally above the low-stage ship's bottom toward the outboard therefrom while a dome B is projected downward rather toward the bow on the middle-stage ship bottom 1b. An upper-stage ship bottom 1c is provided in a pair, one on the right and the other on the left on different levels rather above the middle stage ship bottom 1b toward the outboard therefrom while a dome C is projected downward toward the hull center of the upper- stage ship bottom 1c. With such an arrangement, the domes A, B and C projected on the low-stage ship's bottom 1a, the middle-stage ship bottom 1b and the upper ship bottom 1c respectively are positioned shifted sideways on the ship to eliminate the interference between audio equipment while by no means disturbing the flow of water along the ship's bottom.