User blog comment:StrawHatDavid/A Few Things No One Metioned/@comment-5888163-20130418153122

I think when he mention Tidal Wave he is talking about the marines that is on the island. DD knew of this because Vergo wasn't the only person to have join the marines by DD's order so he must've been warned by what the Marines are planning to do. So that ship bellamy is talking about is maybe their ticket to safety to get away from that island once the marine begun to attack.