Field observation of an ocean sunfish.

If I had stared until it made sense I would still be there now, rooted to that Cornish headland, rain-washed and blinking at it all. Blinking at its fin, a blunt triangular paddle, the same pallid colour as the rain that had swept over the bay in waves all day. Flapping with, I don't know what, the tremor of the waves or the pleasure of a fish half out of water in the rain.

The waves washed it away. The fin disappeared in the grey dip between crests, only to surface a few feet further out. Fin and face, like a wind caught plastic bag drifting endlessly out to sea. I looked it in the eye, through rain-glazed binoculars, big and black and round. A plug-hole, soullessly expressive of depths and darkness unimagined. Unimaginable.

Ocean sunfish. Ocean-coloured sunfish. I knew it only by reputation. World's biggest bony fish, world's biggest niche creature. A once rare drifter in the warm water currents that now run like a river past the Cornish coast. I read later that it eats jellyfish and can reach a tonne. But it doesn't look like that to me. It looks like nothing I have ever seen before – much less understood.

Ocean sunfish, public domain image by Per-Ola Norman