Cocoon

It is everything you've dreamed of.
It is nothing you expect.

A group of trespassing senior citizens get more than they bargained for when swimming in the neighbors' pool restores their health and gives them youthful vigor. Unbeknownst to them, a group of Antareans on a search-and-recover mission to retrieve twenty cocoons containing their crew mates from the ocean floor are renting that house and using the pool to store their cocoons, and when the two groups come together, everyone involved has to make major decisions that will affect the future for all of them.

Not to be confused with another Cocoon.

Tropes used in Cocoon include:

Aliens in Cardiff: Well, Coral Gables, FL.
Alien Lunch: Sort of. In the second movie, Jack and Kitty eat at a restaurant, with bad results for Kitty.
Atlantis: Walter thought it would be the perfect spot for their first base here on Earth.

Walter: Everyone else said, "use the North Pole", and I said, "no, too cold". Sinking never occurred to me.

Ancient Astronauts: Guess!
Distracted From Death: Rosie dies in the first movie when Bernie leaves her side just long enough to get some pills and water for her.
Ditto Aliens: The Antareans, to such an extent that Kitty can easily impersonate Phil in the second movie.
Dramatic Alien VTOL
Dyeing for Your Art: See: Older Than They Look below.
Enforced Method Acting: the scene where Hume Cronyn's character punches out the orderly wasn't all acting. Cronyn, who was a Golden Gloves boxer and lacked sight in one eye, actually knocked the guy out because he (Cronyn) lacked depth perception.
Flying Saucer: Of course!
Fountain of Youth: By way of the pool the Antareans set up for their cocoons.
Full-Body Disguise: The Antareans.
G-Rated Drug: Jack and Kitty's dinner in the second movie ends badly.
G-Rated Sex: Antareans have sex by "sharing themselves" (exchanging energy). Evidently it's "very fulfilling".
Healing Hands: Kitty fixing Jack's broken foot.
- In the second movie, Joe gave up his life energy to save Alma's life.
Humanity Is Infectious: Walter, when the newly-uncocooned Antarean dies in his arms. For the first time in his very long life, he cries.
In Name Only: The first movie was based on an unpublished novel, which was eventually published as the film's Novelization. Aside from the names of the characters, it's pretty different. The second movie's novelization followed on from the plot of the first, diverging even further from the plot of the movie it was ostensibly based on.
Innocent Aliens: When one of the cocoons dies, Walter confesses to Ben that he has never lost anyone close to him before.
Interspecies Romance: Jack and Kitty, again.
Intoxication Ensues: Some human foods don't agree with Antareans!
Mayfly-December Romance: Have we mentioned Jack and Kitty? I'm pretty sure we have.
Mohs Scale of Science Fiction Hardness: Pretty soft.
Motherly Scientist: Sara, in the second movie, acts this way towards Phil.
Never Trust a Trailer: The teaser trailer for Cocoon II: The Return is made up of recycled footage from the first film plus a scene of Jack on his boat that never appears in the actual movie. And Jack has a different boat in the movie, too.
Older Than They Look: The Antareans.
- Inverted by Wilford Brimley, who was only fifty years old when the first movie was made. He had to have his hair colored white to look old enough to be a senior citizen!
The Peeping Tom: How Jack discovers that Kitty is an alien.
Phosphor Essence: In their true forms (after taking off their human disguises) the Antareans glow brightly.
Precision F-Strike: Ben, when they discover that the neighbors are aliens: "Open the f**kin' door, Lefkowitz!"
Real Life Relative: Joe and Alma Finley are played by real life husband and wife Hume Cronyn and Jessica Tandy.
Shout-Out: "May the Force be with you!"
- In the DVD Commentary, Ron Howard mentions asking George Lucas for permission to use that line. Lucas let him use it because, "you were good in American Graffiti".
Stay with the Aliens: Ben and Mary, Alma and Joe, Art and Bess.
Take Me to Your Leader: Reversed when Ben gets Pillsbury to take him to see Walter to negotiate the use of the swimming pool for himself and his friends.
They Would Cut You Up: Said almost word-for-word by Jack in the second movie when a team of scientific researchers manage to get their hands on a cocoon.
Time Abyss: The Antareans, again.

Walter: Every ten or eleven thousand years or so, I make a terrible mistake.

Trailers Always Spoil: One trailer explicitly revealed that Walter, Kitty, et al were aliens.
Two-Person Pool Party: Jack and Kitty, yet again.
We Are as Mayflies
Your Cheating Heart: Joe Finley.