by yshish moderator, translator
It must be a huge guy at the end of those tentacles! 😃
by jo.irisson translator, scientist
Probably a Pelagia noctiluca. Their cup is typically form 10 to 20 cm in diameter and the tentacles can be several m long.
I explored the adjacent frames just above & 5 frames below - never saw the body, but tentacles suggest the body is to the left... 😃