Mark Turns His Houseboat into a Spaceship - Kid's story

In this kid's story, Mark lives on a houseboat that has a lake inside with some fish. An octopus guards the fish, but while the octopus is not looking, some more sea creatures board the ship, forcing Mark to expand the houseboat into a buildingboat and then a rocket ship. Mark then uses the rocket ship to go on an adventure in space.