This is mostly a paste from wikipedia about these jellyfish (and a test to make sure Eachday formats a long item description well)

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It turns out that these jellyfish-like creatures are a part of the Phylum Cnidaria (nigh-dare-e-ah). They are known commonly as “sail jellyfish” or “by-the-wind sailors”, and scientifically as Velella velella. (Velum, from the latin for sail). They have blue-pigmented body tissues and can grow up to 10 cm in length. Other members of this Phylum include the Portuguese man-of-war (Physalia), true jellyfish, sea anemones and corals, representing over 10,000 species worldwide. All of these are invertebrates (animals without backbones).

Velella are thought to be colonial animals. Colonial cnidarians are made up of many individuals (or “zooids”) all attached to the same digestive cavity. Each individual is specialized for a specific task such as feeding, reproduction, prey capture or defense. Quite the collaborative effort!

Found in temperate and tropical seas around the world, Velella are open-ocean dwellers. Gas-filled cells enable them to float and attached to their upper surface is a sail-like flap that catches wind currents for locomotion. Some scientists suggest that Velella grow with their ‘sails’ oriented either to the left or to the right and that this may determine the direction in which they ‘sail’. Because they lack swimming ability, Velella are at the mercy of ocean currents and wind directions.

Velella generally wash ashore in high concentrations every few years during the spring and early summer months. Strong on-shore winds and big swells seem to precede these events. It has been several years since the last time they showed up on local beaches and it could be several more before they return again.

Velella feed on invertebrate eggs and plankton. They have a large central mouth on their underside, surrounded by reproductive stalks and tentacles. Stinging cells (or “nematocysts”) are embedded in their tentacles and are used for capturing prey and for defense against predators. Although not dangerous to humans, some sources claim that touching Velella may cause mild skin irritations. Their predators include sunfish (Mola mola) and also small marine gastropod snails called violet snails (Janthina janthina). Violet snails actually eat the ‘sailors’ as they float along together.

(looks like it formatted just dandy)