by-the-wind sailor

The float is a flat, blue oval disc up to about 10 cm long, topped by a thin sail, usually described as triangular, set diagonally across it; short blue tentacles hang from its rim.

The sail of Velella velella helps it drift at an angle to the wind and occurs in two opposite forms. According to the US National Park Service, left-handed forms are usually found in the Northern Hemisphere and right-handed forms in the Southern Hemisphere; this is a general pattern, not an absolute rule.