Violet Sea Snails

By Maureen Wyer

Finding a purple shell on the beach is surely a rare treat. In all the beachcombing adventures I’ve had over the years in my home “down under” in Sydney, Australia, I have found only a handful of these beauties.

In seeking out a little more information about these tiny and stunning shells, I have discovered that they are not so rare after all. They are a marine snail known scientifically as Janthina janthina, also referred to as the Common Purple Sea Snail or Violet Sea Snail. They can be found all over the coast of Australia, as well other parts of the world where there are warm waters.

While most marine snails live on rocks or the seabed, these purple snails live their life floating in the ocean in colonies of up to a hundred. The snails produce a raft of mucous-covered air bubbles to float and anchor themselves using their foot—only one of ten species that create their own raft!

While they can grow up to 3 centimeters (1.2 inches), the shell is extremely fragile and the underside is a rich dark purple for camouflage as they float upside down. This keeps them less visible to predators such as fish and sea turtles.

These unique snails are dependent on the wind and water currents to move and they feed off a variety of jellyfish, including by-the-wind-sailors (Velella velella) and—the curse of Australian beachgoers—the bluebottle jellyfish or Portuguese man o’ war (Physalia physalis).

Not so fun fact: The Bluebottle jellyfish is responsible for at least 10,000 human stings in Australia each summer, so the violet sea snail is a welcome addition to our waters.

Beachcombers can get lucky and sometimes find them washed ashore, particularly during summer and after onshore high winds. They can be shattered amongst a high-tide line of bluebottles, a common sight at Australian beaches.

Most of the shells I have found and photographed are dead and empty. But beachcombers beware, if you find an intact Violet Snail, the live squishy animal can ooze a purple ink and can stain anything or anyone that interferes with it. The ink may also be a dark blue if it has recently snacked on a bluebottle jellyfish. However, this purple bluish ink is the very ingredient that gives these shells their beautiful purple hue. 

I hope you find your own purple treasure wherever you are in the world.

Learn more about seashells

Learn more about identifying shells, the history of seashell collecting, great shelling beaches, and the lives of the animals who make the shells we find on the beach. Articles ›

No live shelling: Be sure shells are empty and sand dollars, sea stars, and sea urchins are no longer alive before you bring them home.

This article appeared in the Beachcombing Magazine March/April 2022 issue.