Azerbaijan National Academy of Science

U.S. scientists observed the so-called sea butterfly - actually an aquatic snail - using high-speed video and flow-tracking systems.

The 3mm critter flaps its wing structures, which grow where a snail's foot would normally be, in a characteristic figure-of-eight pattern.

It also uses some of the vortex-making tricks that keep insects in the air.

"It looks like it's flying, like a very small insect," said Dr David Murphy, a mechanical engineer at Johns Hopkins University.

Limacina helicina is a bizarre-looking predatory mollusk which, when not displaying its swimming prowess, makes large webs of mucus to filter-feed on smaller plankton.

Its insect-like acrobatics are "a remarkable example of convergent evolution", the researchers write. In other words, the same trait has evolved more than once in completely independent lineages.

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