They move across the ocean with their distinctive transparent "sail" catching the wind, visible in this first picture.
Every now and again a change of wind direction (like the cold blast we are currently experiencing) blows thousands of Velella helplessly towards the shore.
This second picture shows the underside of the Velella where its feeding tentacles are visible.
The same sort of weather that was responsible for the stranding of the Velella brought waters rich in nutrients that has allowed the Diatoms to bloom along the surf of Beach One.