This is a wart comb jelly video.
Translated from Ecomare museum on Texel island in the Netherlands:
A beach full of comb jellies – 08-01-15
Also in winter comb jellies wash ashore. Sometimes very many of them, like on December 23, when the beach at beach post #33 on Texel was filled with hundreds of wart comb jellies. …
Wart comb jellies are from America. Probably they come along in the ballast water of ships to Europe. Since 2006, they are found in the North Sea, Baltic Sea and Wadden Sea.