Alien lifeform?

Given the beautiful weather, an on the advice of a seasoned holiday maker, we went to the beach on the other side of town. The tide was out, leaving a vast expanse of golden sand with very few other people around. We did find a fair few stranded jelly fish, including this massive specimen. It's a barrel ( or dustbin lid) jellyfish huge, alien-like and weird to look at. Hopefully it will have re floated on the incoming tide