Solvin Zankl / By-the-wind sailor (Velella velella) colony. Sargasso Sea, Bermuda.

Flip Nicklin / By-the-wind Sailor (Velella velella) jellyfish, on water surface

Solvin Zankl / By-the-wind sailor (Velella velella) colony, Sargasso Sea, Bermuda.

Solvin Zankl / By-the-wind sailor (Velella velella) colony from underneath Sargasso Sea, Bermuda.

Jean E. Roche / Mass of By-the-wind sailor (Velella velella) jellyfish washed up on beach, Camargue, France, May.

Jean E. Roche / Mass of By-the-wind sailor (Velella velella) jellyfish washed up on beach, Camargue, France, May.

Jean E. Roche / Mass of By-the-wind sailor (Velella velella) jellyfish washed up on beach, Camargue, France, May.

Juan Manuel Borrero / Illustration of individuals of Velella (Velella velella) siphonophore Colony. Velella is a small hydrozoan, 1 to 5 cm which floats on the sea. Pencil and watercolor painting.

Nick Upton / A dense flotilla of By the Wind Sailor jellyfish (Velella velella) of all sizes from a few mm to a few cms on Mediterranean sea surface near the coast of Corsica, France, May

Nick Upton / A dense flotilla of By the Wind Sailor jellyfish (Velella velella) of all sizes from a few mm to a few cms on Mediterranean sea surface near the coast of Corsica, France, May

Nick Upton / Close up view of By the Wind Sailor jellyfish (Velella velella) ranging in size from a few mm to a few cms on Mediterranean sea surface near the coast of Corsica, France, May

Pete Oxford / By-the-wind Sailor (Velella velella) group and other animals washed up on beach, North Stradbroke Island, Australia