By-the-Wind-Sailors by the Thousands

A few days ago at high tide we found these transparent 'things' on the beach:

We wondered what they were. The next day at low tide they were revealed as the framework of By the Wind Sailors, scientific name Velella velella.

By the Wind Sailors are a colony of tiny animals who float together, the By the Wind Sailor has a mass of tentacles - seen here as a dark blue edge - that would hang down in the water and catch plankton. They can't move themselves around but are blown by the wind and washed around by the currents. After the strong northerly winds we've had there was a mass stranding of these on the beach.

They are related to Blue Bottles, I found one of these on the beach too. But only one amongst the thousands of By the Wind Sailors.

Blue Bottles sting, but apparently By the Wind Sailors sting won't hurt people.

Obviously the seagulls didn't mind either, in fact they were having a good feed. What looks like blue-grey stones in this picture are all By the Wind Sailors.

I've posted my sighting on iNaturalistNZ, a great website for sharing interesting observations about the natural world.