About 10,000 years ago, peaceful aliens from the planet Antarea established an outpost on Earth, on Atlantis. When Atlantis sank, 20 aliens were left behind, kept alive in large rock-like cocoons at the bottom of the ocean. A group of Antareans have returned to collect them. Disguising themselves as humans, they rent a house with a swimming pool and charge the water with "life force" to give the cocooned Antareans energy to survive the trip home. They charter a boat, the
Manta III, from a local captain named Jack, who helps them retrieve the cocoons. Jack spies on Kitty, a beautiful woman from the team who chartered his boat, while she undresses in her cabin, and discovers that she is an alien. After the aliens reveal themselves to him and explain what is going on, he decides to help them. Next door to the house the Antareans are renting is a
retirement home. Three of its residents, Ben, Arthur, and Joe, often trespass to swim in the pool. They absorb some of the life force, making them feel younger and stronger. Eventually caught in the act, they are permitted to use the pool by the Antarean leader, Walter, on the condition that they do not touch the cocoons or tell anybody else about it. Rejuvenated with youthful energy, the three men let the pool's advantages take hold as they were relieved of their ailments. Kitty and Jack grow closer and decide to make love in the pool. Since she cannot do so in the human manner, she introduces him to the Antarean equivalent, in which she shares her life force energy with him. The other retirement home residents become suspicious after witnessing Mary, Ben's wife, climb a tree. Their friend Bernie mindlessly reveals the pool's secret to the other residents, who rush to the pool to swim in its waters. When Walter finds them damaging one of the cocoons, he ejects them from the property. The Antareans open the damaged cocoon, and the creature inside shares his last moments with Walter. That evening, Bernie finds his wife Rose has stopped breathing and carries her body to the pool to heal her, only to be informed by Walter that the pool no longer works due to the other residents draining the life force in the rush to make themselves young. Walter explains that the cocoons cannot survive the trip back to Antarea, but will be able to survive on Earth. With the help of Jack, Ben, Arthur, and Joe, the Antareans return the cocoons to the sea. The Antareans offer to take residents of the retirement home with them to Antarea, where they will never grow older and never die. Most of them accept the offer, but Bernie chooses to remain on Earth. Upon leaving, Ben tells his grandson David that he and Mary are leaving for good. As the residents are leaving, David's mother, Susan, finds out about their destination and drives to the retirement home, where they find the majority of the rooms vacant and contact local authorities. While the police are searching for the residents in the dark, David notices Jack's boat being started, with the Antareans and the retirement residents aboard. He runs toward it as fast as he can, and as the
Manta III pulls away from the dock, leaps across the gap, clings to its side, and is pulled aboard by Ben. The boat is chased by the Coast Guard, so with little time left, David says goodbye to Ben and Mary before jumping into the sea. The Coast Guard boats stop to pick him up, giving the others a chance to get away. A thick, mysterious fog appears suddenly, stranding the remaining Coast Guard boats and causing the
Manta III to disappear from their radar, so they call off the chase. As the Antarean ship appears overhead, Walter pays Jack for his services and his boat. Jack embraces Kitty for the last time, and they share a kiss. He then says farewell to everyone before jumping into an inflatable
life raft as the
Manta III rises into the Antarean vessel. Jack watches as it disappears inside the ship and departs. Back on land, a tearful memorial service is held on a beach for the missing residents. During the sermon, David looks toward the sky and smiles. ==Cast==