that's a big jelly
as compared to my sandal. if you look closely you can see the tentacles stretching out far from the main body.
when we went paddling in the bay we saw dozens of fried egg jellyfish (Phacellophora camtschatica), many of them over two feet in diameter. the next morning at low tide, i found several that had washed ashore. onshore they don't show well, but in the sea they really do look like a white egg with a dark yellow yolk.