The tide isn’t always out far enough to go rock pooling, but on a windswept north coast beach like Mawgan Porth there’s always something interesting washed up on the tideline. Junior and I wander through the dunes to the soft sand of the upper shore just after the tide has turned with a plan to look for shark and ray egg cases (mermaid’s purses). We often take them home to soak so that we can check the species and record our finds on the Shark Trust’s Great Eggcase Hunt website.

We both see it at the same time. A greenish lump is shifting at the edge of the retreating sea, being nudged in and out by surging waves. From a distance it could be a stranded animal, but we quickly decide it’s a net and run towards it for a better look.

Currents run fast across the bay and can easily catch you unaware, so I leave Junior behind while I attempt to drag the net clear of the waves. It’s several metres wide and is weighed down with water and sand. With an eye on the sea, I stagger backwards a few centimetres with each heave until the net is clear of the waves.

While I catch my breath, we examine the net close-up. Much of it is encrusted with seaweeds and hydroids. It looks as though it has been in the sea for some while. Attached to one of the intersections is a stony lump like a tooth. This is the ‘skeleton’ of a Devonshire cup coral.

I’m thinking about how to detach the coral without breaking it when I spot a couple walking across the beach towards us. They look like able recruits, so I ask if they might be able to help. The four of us grab the net between us and tug it behind us, army fitness-test style. We take a few breaks along the way, take a small detour to avoid a stranded barrel jellyfish because it doesn’t feel right to run it over. We’re all getting unseasonably warm, but we don’t give up. As we near the top of the beach another woman joins us for the last push to the rubbish collection point.

I take a few minutes to look over the net and find several more cup coral ‘skeletons’. Without a knife it’s not easy to remove them but I manage to prise a few off to show my net-hauling team. To my delight one cup coral has a bump on the side of it. This is an Adna anglica barnacle which only grows on cup corals.

We walk back along the strandline, picking up lots of stray pieces of netting. The plastic fibres are everywhere, breaking into smaller pieces that will stay in the sea for an incredibly long time if they aren’t removed.

There are a couple of lesser spotted catshark eggcases among the seaweed and a ‘by the wind sailor’ hydroid. Then I give such a squeal of excitement that an old couple walking near us turn to stare. When I pick up a transparent piece of jelly that looks like plastic, they turn away again.

The creature fits neatly in the palm of my hand and glistens in the light and feels solid, even though it is entirely transparent. We turn it back and forth, looking through both ends of its tubular, barrel-shaped body. It’s no longer alive, but this is definitely my first salp.

Salps are tunicates, relatives of the sea squirts we find attached to rocks on the shore. They swim actively by contracting their bodies and some salps join together to form long chains. There is a species of amphipod (an animal like a sand-hopper) that is often found sheltering inside them, but this one is empty.

Junior names the salp Cecil. At home he rinses it in water before we take photographs of it. He then prepares a jar of salt water to place it in.

As soon as Cecil is in the water ‘he’ becomes near-invisible. This salp would be perfectly camouflaged in the sea, hiding in plain sight from predators.

At the end of our morning’s endeavours we have a remarkable collection of curiosities set out on the dining table. We have also left the beach cleaner than we found it. A perfect day’s beachcombing.

Huge thanks go to our team of net pullers from St Austell and Milton Keynes!