Unknown Jellyfish Bloom

I was on a Boat off the Coast of Bellaria Igea Marina in Italy when i stumbled across a Bloom of some Mysterious Type of Jellyfish. Despite being a Jellyfish Expert myself, i couldn’t recognise what Species they were. There were around 50, some Small sized ones and many Large ones with extremely Long Tentacles but a small and narrow Bell at the Same Time. They were around 50cm under the Surface. Was it possibly Mawia Benovici? Or a unknown Species that we don’t know about yet?