This tiny snail looks like just a colored dot in the ocean, but under a microscope the reason for its name, “sea butterfly,” becomes clear. Most snails move by pushing a muscular foot against the sea bottom. But the “foot” of this snail, Limacina helicina, has evolved into two flapping appendages that deserve to be called wings, researchers report this week. Usually, the snail is quite hard to find, but its populations boom during a few weeks each year. And its size varies: The snails grow to just 4 millimeters long in the north Pacific, but reach 14 millimeters off Antarctica. It moves up and down the water column quite fast for such a small creature. To find out how, researchers trained four high-speed video cameras on one 1.5-cubic-centimeter spot in a saltwater aquarium containing some of the smaller snails. They added lots of microscopic reflecting particles and used a laser to make the particles visible. Then they waited, hoping a snail would swim into view. Three snails did, providing the team with a close-up, slow-motion look at how they moved and stirred the surrounding water. Most sea-going microorganisms use their appendages as paddles to push against what feels to them like a thick stew. But the sea butterfly “flies” (see video), generating lift by rotating its wings and body in a figure 8, almost clapping the wings together at the top of the stroke—just like a small flying insect, the team reported in the Journal of Experimental Biology. Some of the researchers are now testing whether the larger Antarctic snails swim the same way, and one is trying to build a flying robot that mimics the mollusk’s efficient technique.