There is a movie with a character walking on a beach and we see the real life beach organisms move under the sand

The story of a group of men, an Army Rifle company called C-for-Charlie, who change, suffer, and ultimately make essential discoveries about themselves during the fierce World War II battle of Guadalcanal. It follows their journey, from the surprise of an unopposed landing, through the bloody and exhausting battles that follow, to the ultimate departure of those who survived.

Set during the Allied invasion of the island of Guadalcanal in the Pacific theater during WWII, this film is based on the novel by James Jones. Keir Dullea is Private Doll, who dreads the invasion and steals a pistol to help him protect himself. Sergeant Welsh (Jack Warden), a caustic, battle-scarred veteran, hates Doll, whom he considers a coward. In battle, Doll kills a Japanese soldier and is filled with remorse, which further angers the sergeant. The next day, an emboldened Doll wipes out an entire enemy machine gun post and begins to feel as sadistic as Welsh. The two must work together to clear away some mines, but as they do, their platoon is surprised by a Japanese raid.

After an all-night graduation beach party, a group of hung-over students wakes up under the blazing sun to find their numbers somewhat depleted. An enormous alien creature has burrowed down deep and anyone foolish enough to make contact with the sand finds themselves at the mercy of a sea of flesh-eating tentacles. Will they ever be able to escape its carnivorous clutches?

We cross the dunes when we go to the ocean, but we never take a real look into this strange landscape. Wild, Desert and Alive! Without any voice-over or commentary, this film brings us to the story of animals, plants living in the dune during one day and one night. An experience of sound and image, for a free imagination!

On the search for weird and amazing creatures living on the seashores... This short movie played before The Thief of Bagdad (1940) during its original run in the cinema.

An experimental science fiction film, loaded with special effects. The story of an insensitive young man who meets an alien from another planet.

Something or someone is attacking people one by one on the beach. Some of them are mutilated, but most of them are sucked into the sand, disappearing without a trace. What is the creature responsible? Where does it live, and where did it come from? And is there any chance of it reproducing? Meanwhile, David Huffman and Mariana Hill are once-almost-married old friends, reunited over the death of her mother on the beach, and searching for clues in the abandoned buildings where they used to play when they were young.

Beach sand transforms into a lush tree-scattered landscape.

Reworked and colored images of people playing at the seashore.