Last fall, fishers in the Adriatic Sea (map) near Venice, Italy, pulled up nets full of hundreds of two-inch-wide (five centimeter), golden jellyfish. Having never seen the jellyfish before, the fishers sent pictures to researchers, who identified the beautiful interlopers as a new species.

About two or three new jellyfish species pop up every year, says Claudia Mills, a marine biologist at the University of Washington in Friday Harbor. However, finding such a conspicuous newcomer in a relatively shallow body of water close to shore is extremely rare, says Stefano Piraino, a jellyfish researcher at the Università del Salento in Lecce, Italy.

Piraino and his colleagues published their description of the new jellyfish—dubbed Pelagia benovici—this month in