Heart-breaking footage shows a captive killer whale laying almost motionless in a tiny pool at Mundo Marino, Argentina's largest aquarium.

Kshamenk, 35, was first brought to Mundo Marino in 1992 after being captured off the Samborombón Bay.

According to Mundo Marino, the then three-year-old orca was found beached on the bay by three fishermen along with three other killer whales.

Kshamenk was then taken to his concrete tank at the aquarium, where he has spent the last 32 years.

Kshamenk's tankmate Belen died in 2000, at the young age of 13, which means he has spent the last 24 years in total isolation from his own species.

Since then, Kshamenk has spent every day in a cramped, shallow pool with significantly restricted movement.

Kshamenk is the last remaining captive killer whale in Argentina.

UrgentSeas, a non-profit organisation advocating to end marine captivity, is campaigning to free Kshamenk and bring him to an open sanctuary with other orcas to socialise with.

A 24-hour timelapse video filmed by UrgentSeas on August 12 shows Kshamenk languishing motionless with his face pointed directly towards the enclosure's gate as though he's asking to be let out.

A spokesperson from the organisation said: "We continue to work with Argentinian activists and members of Congress to try to highlight and address his cruel world."

"He needs to be removed from his tiny concrete tank and to join other members of his species before it's too late."

Despite the "Blackfish effect," which was a surge in awareness and activism for captive orcas after the 2013 documentary aired, Kshamenk slipped through the cracks."

Mundo Marino was contacted for comment.