Velella

By-the-wind sailors are the teacup-sized blue ovals that sometimes carpet West Coast beaches by the thousands. Each one is a floating colony of specialized polyps rather than a single jellyfish, and it travels by a stiff, clear sail standing about an inch above the water, so the wind decides where it goes. Most West Coast strandings happen in spring, and big strandings have followed warmer winters that let their numbers spike offshore. Their short tentacles catch plankton and larval fish, but their stinging cells cannot harm people, which makes a blue tide line of them one of the easier mass strandings to enjoy. Look rather than handle them all the same.