ORIGINAL: pl_09
It is up to you to figure it out since I already included its

internal photos
A boat this small theoretically could dive using RCABS but I don't see any bladders on the video so I think you're using a small water pump with a vented tank.
Have you seen this Japanese modeler's Typhoon. It uses a gas system with a lighter as the gas reservoir
http://babelfish.yahoo.com/translate...s&fr=fptb-msgr