They look like jellyfish but ctenophores (comb jellies) are totally different animals that have their own phylum. Ctenophores don’t sting but use sticky cells to catch their prey. They swim using comb plates made of tiny hairs (cilia) fused together. The beautiful rainbow colour patterns visible here are caused by refraction of light in the glass-like comb plates acting like a prism. Some species also produce light themselves.
Pleurobrachia pileus, Wadden Sea, NL.Pleurobrachia pileus, Wadden Sea, NL.Pleurobrachia pileus, Wadden Sea, NL.Pleurobrachia pileus, Wadden Sea, NL.Pleurobrachia pileus, Wadden Sea, NL.Pleurobrachia pileus, Wadden Sea, NL.Larva of Pleurobrachia pileus, Grevelingen, NLPleurobrachia pileus, Grevelingen, NLPleurobrachia pileus, North SeaPleurobrachia pileus, North SeaBeroe gracilis, Grevelingen, NLBeroe cucumis, Wadden Sea, NL.Beroe cucumis with ingested Pleurobrachia pileus, Wadden Sea, NL.Beroe cucumis, Wadden Sea, NL.Beroe cucumis, Wadden Sea, NL.Beroe cucumis, North Sea.Larva of Mnemiopsis leidyi still in the egg, Grevelingen, NLMnemiopsis leidyi juvenile, Grevelingen, NLMnemiopsis leidyi, Wadden Sea, NL.Mnemiopsis leidyi eaten by Beroe gracilis, Wadden Sea, NLMnemiopsis leidyi, Wadden Sea, NL.Mnemiopsis leidyi, Wadden Sea, NL.Mnemiopsis leidyi, Wadden Sea, NL.Bolinopsis infundibulum, North Sea