There is a wealth of interesting wildlife by the sea, says Eanna Ní Lamhna. Here’s her guide to the creatures who live by the shore.  

Sandy beaches are swept by the tide twice a day. Each tide brings in all sorts of wildlife and deposits it along the high tide mark. You never know what a walk along the tide mark, with your eyes peeled, will reveal. There are always shells. Sea shells are the homes of sea creatures that belong mainly to the same group as the snails in our garden do. These creatures live in the sea, generally attached to rocks or seaweed or buried in the mud or sand below. When they die, their empty shells are washed up on the beach. 

Sea creature fall broadly in two groups. Bivalves have two shells, which they keep tightly closed when not feeding. When they are covered with a flowing tide, they open the shells and filter in all the tiny little bits of plankton which are their food. Oysters, cockles, mussels, clams, razor shells and scallops all belong to this group. It should be easy to find at least one half of the pair on your walk along the high tide mark. Finding a matching pair is more difficult. These are all edible when we buy them in the fish shop and they are still alive. Do not be tempted to try eating any you might find still tightly closed on the beach. They are long dead and would make you very ill if you tried to eat them.

The second group is made up of shells which are complete in themselves. It is fun to hold a big whelk shell up to your ear like a telephone and listen to the sea through it. The original occupant of this shell, a dog whelk, is a predator and will drill a hole in limpets and suck out the contents. Limpet shells are like cones, and you should be able to find some of these, as well as periwinkle shells which look very like black roundy snail shells. Again, these are edible when sold to you at a winkle stall, complete with a pin to winkle out the tasty salty morsel. Actually, these periwinkles come in a variety of colours – orange-red, grey, white as well as black, so see what kind of an assortment you can find on your beach. 

You may find a washed-up jellyfish among the seaweeds. The usual one – about the size of a fried egg - is the common jellyfish. This has a transparent jelly-like body, and you can see four purplish horse-shoe marks as you gaze down at it. These are its reproductive organs. This particular jellyfish rejoices in the Irish name – Smugairle róin – seal’s snots. While it is now dead, and the smooth flat top can do you no harm, do not be tempted to pick it up with your hand. If you turn it over with your shoe or a stick, you will see that it has long strands attached to the underside. These are where the stings are, they trail out behind the jellyfish when it is swimming, and it catches its food by stinging and killing it. Even though the jellyfish is now dead on the beach, the strands will still have working stings so beware. 

But if you are on a really good area of coastline, there may well be a rocky part of the beach where there will be rock pools when the tide is out. This is where to go with your bucket and net if you want to meet some living sea shore animals. A good rummage among the seaweed should soon dislodge any small shore crabs that were trying to keep a low profile, so use your net to scoop one into your bucket of seawater for examination. Crabs are crustaceans – and they are hungry predators. They have ten claws – eight for walking on – they can only move sideways as you will see when you release it back again. The two front claws are what they use to catch  prey and they are very quick with these, so mind your fingers. The colour can vary, as the crab uses the seaweed as camouflage - they can be yellow, brown, dark green or even black. 

Another rummage in the rock pool may reveal a whelk shell with something living in it. You will notice the shell apparently moving by itself. It is safe to pick it up and look in. What you will see is a hermit crab which has squatter’s rights here. A hermit crab has no strong back shell of its own like a shore crab has. It must find an empty whelk shell and reverse into it and wave its hunting claws out at any possible prey. You won’t be able to prise it out without killing it, so once you have marvelled enough put it gently back. 

If your rock pool is only uncovered at low tide, you might be lucky enough to find a starfish. Usually these have five arms, with an eye at the end of each one and their mouth is at the centre of the underside. These feed on bivalves such as mussels. They force them open with their strong arms and then their stomach comes up out of its mouth, goes into the opened shell and digests the exposed contents directly. You would never think, looking at it lying there, that it could do such grisly things.

A fairly deepish rock pool, one that comes up to your knees, may well have living things stuck to the sides. Among the limpets you may be lucky enough to find a sea anemone. While this can just look like a red lump of jelly if it is above the water level, it really changes dramatically when covered in sea water, so go and look a bit deeper. Here you might find one in full hunting mode. It will have unfurled a ring of tentacles at the tip and be filtering the surrounding water, directing the juicy plankton bits into its mouth at the centre of the ring. It actually looks more like a flower than an animal, but then appearances are often deceptive. 

And of course, there are all the seaweeds that you might find both on the shore and in the rock pool. These are all plants and they come in three colours. Green seaweeds are small and stringy and are usually furthest from the sea. Most of the tideline consists of the brown seaweeds, various wracks with air bladders along the fronds, which kept them upright when they were growing attached to rocks on the seabed by their holdfast at the end. If you are lucky, you might find a big flat strap of kelp. Bring it home with you and put it in your next bath. It works wonders for your skin and you can always bury it in the flower bed afterwards, where it will do wonders for the fertility of your soil too.