what I have learned today: to know the by-the-wind sailor

What are these things? They wash up on the beach in droves, are from one to half-a-dozen centimeters long, and come up if you google for beach blue diagonal sail.



They are Velella velella, the by-the-wind sailor, a colonial coelenterate like Physalia physalia.

http://www.cornwallwildlifetrust.org.uk/nature/marine/velella.htm

They exist in two forms, either left- or right-handed. The wind tends to distribute them into groups, depending whether they are either left- or right-handed, so strandings tend to be made up of one group.

http://jellieszone.com/velella.htm

Beneath the float is a grouping of several types of zooids, colored brown by the presence of zooxanthellae. A large central mouth is surrounded by shorter reproductive stalks with mouth openings that bud tiny adult medusae that produce eggs and sperm. [...] Dangling beneath the rim of the float are hollow tentacles that ensnare fish and invertebrate eggs, copepods and appendicularians.

Also,
http://www.pbs.org/odyssey/voice/20020407_vfts_transcript.html

Right whales sail by holding up their tails and letting the wind blow them along, but they seem to do this only as a form of play.