What are they?

I may have lived by the sea for several years now but I'm still not very good at naming marine life. I found this walking on the beach today. A bit of flotsam that had been washed up. A fish-shaped sand castle builder I'm guessing. As you can see, Sturla beach isn't exactly the best place to find sand.

So, what are the little things floating around inside it?

If you're wondering what the little blue things on the surrounding pebbles are, they're jellyfish. You can see a better photo I took of them last year here.