Most kitesurfers here wear thin synthetic body suits that leave only head, hands and feet exposed. The suits are for protection from jellyfish stings. On about half of my beach walks I see a few washed up jellies, sometimes more than a few. But never have seen enough beached dead jellies for me to imagine this was possible:
The population density in the photos is misleading. The jellies are sheltering on the lee side of a pier, that is, on the side that is both downwind and down current. Jellies float with the wind and current, though they can propel themselves against both if need be. Here I watched jellies drift beneath the pier one by one, then join the fluther* by occasionally moving up current to keep themselves in the wind and current shadow of the pier.
* Searching turned up various collective nouns for jellyfish, with ‘fluther’ and ‘smack’ appearing most often. Some use the term ‘smuck’ which is perfect for PB&J fans.