In this report, the authors discuss the following three items. Firstly, the method for estimation of the behavior and performance of the floating terminator OWC type wave power convertor are discussed in this paper. The convertor is moored at the offing and it can absorb the wave energy, convert it to a different form of energy, and create a calm sea area behind the device as a floating break water effectively. Secondly, as an application of this method, authors have designed a new concept floating wave power convertor. It is "the Mighty Whale" and it has several unique behaviors. The outline of this device is introduced. Finally, the concept of utilizing the wave energy, which is converting from wave to compressed air by "the Mighty Whale" is described. The authors propose that the wave power device should be used for improvement of the marine environment, because this energy is renewable and clean.