We weren’t really rock pooling, just going for a walk to the beach, or so we said. Junior packed his hammer and chisel in case there were fossils and I packed my camera, because you never know.

On my last wander at our local beach I had hoped to find some gem anemones to photograph, but didn’t succeed. It was worth another look for these tiny creatures, which have stripy tentacles and bright colours around their mouths when they are open, but at low tide most of them are retracted into white-striped blobs.

I left the sounds of hammering and splitting rocks behind me at the edge of the shore, where Junior was happily amusing himself on a fossil hunt, and headed towards an unseasonably glassy sea, pausing to look for anemones in the small pools on the way.

At the water’s edge, I reached a large pool too deep for gem anemones, but in the middle of the pool a submerged boulder was covered in Irish moss seaweed, providing the perfect habitat for stalked jellyfish. I looked so closely among the tangles of weed, hunting for tiny jellies, that I almost missed the huge stalked jellyfish right under my nose.

This was an unusually large Haliclystus octoradiatus stalked jellyfish, easily distinguished from the other species we see in Cornwall by the presence of blob-shaped primary tentacles in between its arms.

Most stalked jellyfish of this species have just one primary tentacle blob between each pair of arms, but this one had far more blobs than usual. The jelly can use these primary tentacles as anchors to grip onto the seaweed if it chooses to move, using a looping, cartwheeling motion.

In another nearby pool I spotted this colourful Calvadosia cruxmelitensis stalked jellyfish, well decorated with white nematocysts, which are its stinging cells.

Junior joined me at this point, wanting to show me a blenny he’d found. We scrambled nearly to the top of a high rocky outcrop in which some small pools had formed. There was no sign of his little fish, and there were no gem anemones, but there was this daisy anemone.

We carried on our expedition through a gap in the rocks to the adjoining beach where clear, shallow pools lined with pink encrusting seaweed nestled under a towering overhang carved out by the sea into the shape of a breaking wave.

These pools were full of anemones too and we stopped to take photos of clusters of snakelocks anemones and a rather flattened-looking strawberry anemone before I noticed the first gem anemone. It was closed up, forming a diminutive pink blob that blended perfectly into the colours of the pool. Close to it was another.

As we moved among the chain of pools we found dozens, but not a single one was open. Junior stared determinedly into every cranny, excited that the pools he had found were proving so interesting.

“There are some open anemones here,” he called out, “maybe Dahlia anemones? What do gem anemones look like when they’re open?”

I knelt on the rock beside him. At the far edge of the pool, tucked under a small ledge, I could see the white stripes of the gem anemone tentacles. Much cheering and hugging ensued.

Soon I was able to show Junior my up-close photos of the anemones so he could see why I was so obsessed with finding them. Each one had a vivid, almost fluorescent green mouth tinged with bright pink spots at its corners. The anemone’s mouths were framed in deep red and grey rays that stretched to the base of the zebra striped tentacles, some of which had flashes of green at their bases.

Truly one of our most spectacular anemones, people rarely notice the gem anemone because it is only a few centimetres across even when fully grown.

Junior is already planning a night time return to these pools to investigate whether these anemones will glow under the light of our ultra-violet torch. Watch this space!