A rare, all-white Risso’s dolphin delighted a whale-watching crew at Monterey Bay after making an appearance alongside the boat.

The video was shared by Monterey Bay Whale Watch and shows the dolphin, who is affectionately nicknamed Casper, gliding along.

Monterey Bay Whale Watch staff told Storyful that Casper is either albino or leucistic, both conditions resulting in a reduction of pigment.

“The difference between these two genetic mutations is that albino animals have red eyes. Because it’s almost impossible to see Casper with the eyes opened, the mystery is still going on!” they said. Credit: Monterey Bay Whale Watch | Evan Brodsky via Storyful