Trapdoors, under each car. Put the captain in a big twirly seat and give him a red button and a white cat, because everything's better when you're cosplaying as

Trapdoors, under each car. Put the captain in a big twirly seat and give him a red button and a white cat, because everything's better when you're cosplaying as a Bond villain. (Ok, serious question about the portable-barrier-and-pump solution: could there be any chemical risk from using sea water, rather than fresh water?)