Investigating the damage conditions and conducting experiments by use of a model of the oyster raft, it was surmised that the main factor causing damaged to rafts is due to the tension acting on the "suikaren" in the 1st report. In this study, how to reduce this tension is examined. The improvement proposal is very simple and only involves attaching a float in the upper portion of the "suikaren". To investigate the validity of this improvement, "suikaren" and raft prototype models are prepared, and the bending moment acting on the raft portion is measured in regular waves. Consequently, it was confirmed that the bending moment for the improved proposal is reduced by about 30\% as compared to the conventional raft Also the improvement was confirmed by numerical computations based on dynamic simulation model for "suikaren". If this improvement is put into practical use, the culture of oysters can be carried out more efficiently than before.
