Haminoea japonica is a species native to Japan and Korea and recently spread to the Pacific coast of North America as well as into Europe: Atlantic coast of France and Spain, Venice lagoon in the northern Adriatic Sea and Sabaudia lagoon, Fusaro Lagoon and Maremorto lagoon in the Tyrrhenian Sea, presumably with imports of bivalves for commercial aquaculture. During a dive in the lagoon of Fusaro, I observed some specimens of this alien mollusc while laid their yellow egg masses on some green filamentous algae.