Colourful or camouflaged, crabs can live up to 20 years of age

View of the Connemara coast from Mweenish Island tidal pool, Galway
All along the shore there are boulders arranged among turquoise pools, sandy stretches and drifts of storm-severed seaweed, each offering a sheltered nook for intertidal creatures. Rocks are covered in lichens and clingy limpets, where the cleavage shelters predatory periwinkles, whelks and topshells.
The range of colours, even within individuals of the same species, is impressive.