When a large tanker is approaching to her berth in open road under seas and swell, the ship's under keel clearance is decreased by rolling and some troubles on ship handling are introduced. Therefore, it is necessary to estimate the rolling amplitude exactly for keeping good under keel clearance in restricted water. This paper relates to some model experimental investigation about the shallow water effect on ship's rolling in the range of under 10 degrees of amplitude in beam seas. Model tests were carried out for 2 models of a tanker and a cargo ship, and the following results are obtained. 1. the increasing of virtual mass moment of inertia for rolling is remarkable in the depth of water under twice of ship's draft, 2. on the case of ship stationary in beam seas, the rolling amplitude caluculated by uncoupled equation of motion is good agreement with the model test results as shown in figs.5 and 6, except the nearly synchronous motion.
