Sand martin
The tiny, brown-and-white sand martin is a common summer visitor to the UK, nesting in colonies on rivers, lakes and flooded gravel pits. It returns to Africa in winter.
Sand mason worm
This worm builds its own home out of bits of shell and sand. It can be spotted on the shore all around the UK.
Sand sedge
Sand sedge is an important feature of our coastal sand dunes, helping to stabilise the dunes, which allows them to grow up and become colonised by other species.
Sanderling
The sanderling scampers about the waves looking for marine crustaceans, fish and even jellyfish to eat. It visits the UK in winter from its Arctic breeding grounds, but can also be seen as it passes through on migration during spring and autumn.
Sandwich tern
Found around our coasts during the breeding season, the large Sandwich tern can be spotted diving into the sea for fish such as sandeels. It nests in colonies on sand and shingle beaches, and islands.
Saucer bug
An underwater predator, the Saucer bug uses its front pincer-like legs to catch its prey. It can be found at the bottom of muddy, weedy ponds; but handle with care - it can inflict a painful bite!
Saw-wort
Saw-wort gets its common name from the serrated, saw-like edges to its leaves. It is a plant of unimproved hay meadows and woodland edges, its purple, thistle-like flowers appearing over summer.
Scampi
Did you know your seaside scampi was actually a kind of lobster? Traditionally so - although the scampi that is often eaten with chips can be anything from prawns to fish.
Scarlet elfcup
As its name suggests, the scarlet elfcup is a bright red, cup-shaped fungus. It is widespread, but scarce, and can be found on fallen twigs and branches, in shady, damp places.
Scarlet Lady
This brilliant red and white sea slug would make the perfect nudibranch for a Christmas card image or perhaps a football team mascot!
Scarlet pimpernel
Once considered a weed of cornfields, the Scarlet pimpernel is now in decline due to intensive agricultural practices. It can be found in arable fields, on roadside verges and waste ground, and on coastal cliffs.
Scarlet tiger moth
This beautiful moth is often found resting on leaves, though it does also fly during the day.