Giant's eye?

No, I'm fairly sure it's a lion's mane jellyfish (or possibly a compass jellyfish) There were loads washed up on the beach on the far side of the island.

I have always thought that beached jellyfish look like dissected eyes and had a poem I had written on the subject printed on a postcard a few years ago. The poem is here

Moon Jelly

In the sea it shimmers,
a daylight-scuttled satellite
or softly-beating embryonic heart.

But, stranded, it is phlegm:
the product of a chesty cough,
the lime-green marmalade you never liked,
or possibly an eye: the one that Mr Allerdice
dissected for the girls of class 2R,
which oozed a limpid pool of sightless gel.

So that when you find one
helpless and abandoned on the beach
you think of Jane, and of how she fainted
seeing that burst eye,
collapsing like some fragile, southern belle.

And the fascinating clunk her body made,
the dull percussion of her head on wood
as she slithered down, like jelly, from the chair.
And the way we swooped above her, cruel as gulls,
our savage cries of 'sir!' piercing the air.