Marine scientist Fred Miller designs the world's first underwater home, but when the business magnate funding his work threatens to end the project, Miller volunteers to live in it with his own family to prove it's practical. The underwater clan includes his water-phobic wife and his daughter and son, who are part of a rock and roll band. They bring along the lead singer and drummer. Along the way, they have to contend with a competing engineer who promises to mine the ocean floor for the businessman. A record producer likes their music and books them on TV, leading the kids to try to escape to the surface....