Seashores vary enormously from rocky coastlines, shingle beaches, sand beaches to the muddy shores and salt marshes or estuaries and bays. The creatures that inhabit these various types of shores vary just as dramatically.
Shingle beaches probably provide the least favourable environment for wildlife because shingle is made up of vast numbers of loose rounded stones which are unstable and move a lot preventing most forms of life from getting a foothold.
Sandy shores are also unstable, but sand allows various creatures to burrow under its surface. Lugworms, bivalve molluscs such as cockles and razor shells, shrimps and some fish like the Weever Fish can live there.
A rocky coastline allows rock pools to develop. These rock pools can provide a oases for wildlife and creatures such as barnacles, se anemones, crabs, mussels, shrimps, limpits, sea urchins, seahorses and rock pool fish all of which can flourish in rock pools.
In sheltered areas when the force of the sea is minimal, like in estuaries and bays, the very smallest suspended particles are deposited as mud or silt. This silt is high in nutritional value and allows sea creatures such as worms and bivalve molluscs (like cockles) to flourish. These in turn provide food for wading sea birds which often love to feed in large numbers. Many seashore environments and their wildlife are under threat from over use either commercially or recreationally. Care needs to be taken.