Recent model experiments by the authors indicated that bow-diving is one of the crucial capsizing modes for a ship traveling in following and quartering seas with high forward velocity, while only a few research attempts on this phenomenon were reported so far. In this paper, basic features of bow-diving are discussed with measured time series. As a result, it is concluded that bow-diving is associated with surf riding and triggered with submergence of bow bulwark top. Then, by statically calculating vertical distance of bulwark top from wave surface with Froude-Krylov assumption, the possibility of bow-diving observed in the experiment is reasonably well explained.