

It is a hot day and Johnny's family cannot seem to find a place where they can cool off and get wet. They go to Lake Pork-Ness, which is rumored to have a monster inhabitant. Susan and Mary believe that the idea is a total myth and try to prove there are no monsters in the lake.
Johnny and Dukey must help a pathetic pirate, Nobeard, take down his powerful brother pirate, Blackbeard, and impress his father, Greybeard. Johnny goes back to the future to get his sisters' help.