Velella velella Linnaeus 1758

by the wind sailor

 

 
Features Velella consists of a flat oval blue disc surmounted by a transparent, diagonal sail. The disc has many gas filled tubes so that it floats. Around the lower edge of the disc there is a fringe of tiny feeding tentacles, which trap food. These are generally not irritant to people. There are numerous reproductive structures and a centrally located mouth on the underside.
When they wash ashore, they usually do so in large numbers.
Distribution  
Depth surface dwellers
Size about 2cms across