Cocoon

About 10,000 years ago, peaceful aliens from Antarea established an outpost on Earth at Atlantis. When Atlantis sank, 20 aliens were left behind, preserved inside large rock-like cocoons on the ocean floor. The plan was to return later to retrieve them for their journey home.

In the present day, a group of Antareans disguises themselves as humans and rents a house with a pool. They charge the pool water with life force to energize the cocoons for the trip home. Their operation hinges on secrecy.

They charter a boat, the Manta III, from a local captain named Jack who agrees to help retrieve the cocoons. Jack becomes an unwitting ally in their plan. He supplies the vessel and access to deep-water locations.

Jack spies on Kitty, a woman among the team who is undressing in her cabin, and discovers that she is an alien. After the revelation, the Antareans explain the mission and convince him to aid them.

The Antareans reveal themselves to Jack and lay out the plan to gather the cocoons. Jack decides to help them, aligning with the alien goal to return home.

Next door, three retirees Ben, Arthur and Joe discover the pool's vitality and begin using it to feel younger and stronger. Their rejuvenation comes at the expense of the cocoons' energy balance.

Walter, the Antarean leader, allows the others to swim if they do not touch the cocoons or reveal the truth. The deal buys them temporary relief from their ailments.

Kitty and Jack grow closer and decide to make love in the pool. Kitty shares her life-force energy with him, deepening their bond and aligning his loyalties with the mission.

Mary climbs a tree, drawing suspicion from the residents, and Bernie accidentally reveals the pool's secret. The others rush to the pool to swim, escalating the situation.

Walter finds the group damaging a cocoon and ejects the trespassers. The damaged cocoon’s creature shares its last moments with Walter. That night, Bernie finds his wife Rose has stopped breathing and the pool no longer works due to life-force drain.

Walter explains that cocoons cannot survive the trip back to Antarea but will be able to survive on Earth. With Jack’s help, they return the cocoons to the sea, beginning the exodus.

The Antareans offer to take residents of the retirement home to Antarea, where they will never grow older and never die. Most accept the offer, but Bernie chooses to remain on Earth.

Ben tells his grandson David that he and Mary are leaving for good. Susan finds out and drives to the retirement home, only to discover most rooms are now vacant and authorities have been alerted.

David runs toward the harbor in a final attempt to reach the Manta III as the Coast Guard begins pursuit. A thick fog appears and the Coast Guard boats are stranded, allowing the Manta III to evade capture.

The Antarean ship appears overhead as Walter pays Jack for his services. Jack and Kitty share a farewell kiss before Jack jumps into a life raft as the Manta III rises into the ship and departs Earth. A beach memorial is held for the missing residents, and David smiles toward the sky.