More than two decades after spotting a mysterious, gelatinous, bioluminescent creature swimming in the deep sea, California researchers this week announced that it was a new species of sea slug.

A “remarkable” new sea slug nicknamed the “mystery mollusc” has been discovered swimming deep in the ocean’s “midnight” zone. The species has “unique” adaptations for life in the pitch black depths including a large gelatinous hood to trap prey,

It took nearly 25 years for biologists to discover that a swimming and glowing organism in the ocean’s midnight zone was actually a sea slug,” reported The New York Times.