Helpless blob of jelly is a formidable predator

Sandsend, North Yorkshire It's not a jellyfish but a ctenophore, one of a group thought to be more than 500m years old

Close to dead calm on the Yorkshire hem of the North Sea today. The waves are barely 10cm high and the water is so clear that, standing knee-deep between each half-hearted surge, I can see sand grains shifting on the bottom.

There's a commotion further out - cries of warning, then curiosity. Something is collected cautiously in a bucket and brought to me for identification. Even close up against the blue plastic, it's difficult to see clearly - an ovoid emptiness where the sand swirling in the water does not go. Then suddenly, its fringes light up pink, gold and green.