Whole whelks, sea snails, for sale at 99 Ranch Market in Chandler, on June 3, 2021. 99 Ranch Market
San Diego, California – Beachgoers along La Jolla Shores are witnessing a vivid and unexpected arrival: violet sea snails, small and gleaming like polished gemstones, have made a rare appearance along the Southern California coastline. These dazzling marine drifters, known scientifically as Janthina janthina, are almost never seen this close to land. Their sudden presence has sparked awe, curiosity, and scientific intrigue in equal measure.
Typically found far offshore in tropical and subtropical waters, Janthina are pelagic snails that spend their lives floating at the ocean’s surface. Each snail secretes its own buoyant raft made of air bubbles encased in chitin—a structure that keeps it aloft and allows it to drift with the currents. Unlike the slow-crawling mollusks familiar to tidepool explorers, these snails are wanderers of the open sea, tethered not to rocks or reefs but to their delicate, self-made flotation devices.
Their shells, only about the size of marbles, shimmer in hues of deep violet and lavender, making them a stunning contrast against the muted tones of sand and surf. But the color isn’t just a striking visual feature. It serves as a key part of the snail’s survival. The darker upper side of the shell shields the animal from predators above, blending with the shadowed ocean below, while the paler underside helps it evade detection from the fish swimming beneath. The purple pigmentation also provides protection from the sun’s ultraviolet rays—a necessary adaptation for a life spent at the ocean’s sunlit surface.
This sudden shoreline appearance is almost certainly linked to a warm water intrusion that lifted surface temperatures into the 70s late last month. Oceanographic researchers note that similar sightings occurred during the 2015 El Niño event, when an anomalously warm “blob” of water disrupted normal current patterns and carried tropical species farther north. While that previous encounter yielded only a few specimens, this year’s event has brought a surprising number ashore, making it one of the most visible local arrivals in recent memory.
The snails’ visit is likely a fleeting one. Once detached from their fragile bubble rafts, adult Janthina are unable to survive. Their presence on the beach is often a sign that their journey has ended. But their sudden visibility offers a rare opportunity for scientists and the public alike to observe a creature that normally remains hidden in the vast, floating wilderness of the open sea.
Beyond the beauty and novelty, the appearance of these snails is a quiet signal—one that reflects changing ocean temperatures, shifting currents, and the interconnectedness of distant ecosystems with California’s own coast.
