Precious and Granny are on Granny's special surfboard and having fun when a submarine comes up underneath them and the captain invites Granny to tea. This is only a diversion as he and his first mate, Igor, think that the surfboard is some kind of secret weapon.
Igor tries to take the surfboard from Precious while the captain is entertaining Granny, but Precious outwits him every time. He begins to think that Precious is really the secret weapon.
The captain grows impatient and comes up and Precious does to him what he has been doing to Igor. Captain Kook and Igor decide they need to call off the invasion and let Granny return to her surfboard and Precious while they quickly submerge and head for home.