We’ve been planning this trip since our visitors first came to Cornwall a year ago. They’re determined to try rock pooling having missed out last time. This week the tides are perfect. They live near the sea back home in Essex, but they tell me it’s not the same and I can well believe it.

They’ve never seen a starfish in the wild before. My mission is clear.

With picnic and buckets in hand, we set out, treading gingerly over seaweed and searching among the rocks. Within minutes, our friends are putting yesterday’s hasty tutorial on crabs into practice as they try picking them up safely. They score top marks on this and on working out whether the crabs are male or female from the shape of their tails. We find several species of crustacean, including this large squat lobster.

While our visitors search the shallow pools, finding anemones, fish, prawns and hermit crabs, Other Half and I walk out through slippery gullies towards the sea with Junior, taking photos and collecting interesting creatures for our visitors to see. I find a small rock with a beautiful covering of star ascidian.

As I look more closely I see flatworms moving across the sea squirts. They seem to be iridescent, flecked with glowing yellow spots. They have head tentacles, like a slug, with eye spots at the end. They’re fascinating creatures but very hard to identify to species level in the field.

I film hermit crabs fighting over food in the shape of a flat periwinkle. A minuscule shell runs across a rock and I lift it to find a hermit crab with hairy claws (Anapagurus sp.) inside.

In one area there are many shore urchins. They often seem to cluster together like this. I notice one has its tentacle feet out, reaching in all directions.

I collect a cushion star to show my friends but keep looking for larger starfish and brittle stars, knowing that this is what they most want to see. Large edible and montagu’s crabs scuttle around my feet, but I ignore them and keep hunting. As I lift a piece of bladderwrack, a rockling flaps and thrashes, making me leap out of my skin. It swims away and is gone in a second.

As I reach the end of the gully I turn a rock and discover echinoderm heaven. Large brittle stars are walking over the edge of the stone on spindly legs and right in the centre of the rock is a fair-sized spiny starfish.

I worry that I’ve left my visitors alone too long and that they’ll be bored, but I find them still completely engrossed in their search for crabs. They take turns to hold the various starfish and we put the spiny star in the bucket to watch it unfurl its hundreds of tentacle feet.

Our visitors are delighted with all they’ve found and seen. We’re already planning their next trip. And I’m pleased too, both that my friends have discovered the joy of rockpooling and seen starfish, but also that I found a flatworm I hadn’t seen before.

Is it normal to love worms? There are some amazing ones in the Cornish rock pools.