The park opened to the public for the 1977–78 summer season, the same year it acquired its first dolphin, and it grew quickly into something far larger than a rehabilitation center. Today it spans twenty pools and is home to more than fifty marine mammals, over eighty birds, and a crowd of fish and coastal creatures. There are sea lions to feed by hand at the Bahía de Lobos, dolphins performing in the Estadio del Mar, and a penguin shelter that still does the original work: it houses penguins that came ashore to die and were instead cleaned, fed, and rehabilitated. The founder's rescue impulse never entirely disappeared. It simply shared the grounds with the business of the show.

For more than thirty years, the park's most famous resident was an orca named Kshamenk. He arrived in 1992, around four years old, taken from the waters of Samborombón Bay just up the coast. The park said it had rescued him after a stranding and kept him because he could not be released; critics countered that he may have been deliberately driven ashore and held to sidestep Argentine laws against capturing wild marine mammals. Whatever the truth of his arrival, the shape of his life was not in dispute. After his companion Belén died in 2000, Kshamenk lived alone, the last captive orca in all of Latin America, in a tank barely longer than his own body.

In his final years, Kshamenk became a symbol. Drone footage of him lying nearly motionless in his small concrete pool spread around the world, and hundreds of thousands of people signed petitions calling for him to be moved to a seaside sanctuary where he might live out his days in open water. The campaign had a name, Free Kshamenk, and a global reach. It did not come in time. On the 14th of December 2025, Kshamenk died of cardiorespiratory arrest, somewhere in his mid-to-late thirties, after thirty-three years in captivity. He had outlived the typical lifespan of a captive male, which his keepers offered as comfort and his advocates read as indictment. Either way, an animal who never chose any of it spent almost his entire life alone, performing for a species that had decided his loneliness was entertainment.

Kshamenk's death closed a chapter, and it leaves Mundo Marino, and the wider world of marine parks, facing a harder question than it once did. The founder's original mission, to rescue and return, still beats inside the place: penguins are still rehabilitated, stranded animals still treated, and conservation and research are still part of the story the park tells. But the spectacle that drew the crowds, the orca circling a tank too small to turn in, has come to feel like a relic of an older, less examined era. The shore where Méndez first carried wounded animals out of the surf is the same shore where the last of Latin America's captive orcas finally died. What the park becomes next is the question that beach now poses.