In a 2025 study in Frontiers in Marine  Science, researchers announced the discovery of Physalia mikazuki, a new species of Portuguese man-of-war off Japan’s coast. These carnivorous  creatures rely on winds and currents to drift across the water, using their tentacles to trap, paralyze and kill small marine prey. Their sting can be fatal to humans.

Until now, man-of-war were observed in the subtropical waters off Okinawa and the warm temperate waters of Sagami Bay. However, the new species was found on Gamo Beach, in northeast Japan. Scientists believe that rising water temperatures have created an expanded habitable zone, posing safety risks for bathers and ecological concerns for fishermen.