A dolphin, 46 penguins, and hundreds of fish were left at the Inubosaki Marine Park in Choshi, Japan.
The park, just northeast of Tokyo, was abandoned and closed in January, reports Reuters.
Activists in Japan are calling for the animals to be saved after discovering they were still alive.
Images from the park show a bottle-nose dolphin, named Honey, swimming in a small pool.
Park officials cited a decline in visitors after the 2011 earthquake and tsunami for closing.