What Are Those Small Holes in the Sand? (It's Not Always Kids Digging)
Most of the small holes you spot at low tide were made by something living underneath, not a spade
Walk any flat sandy beach or tidal flat at low tide and you'll find it covered in small holes — some perfectly round, some keyhole-shaped, some with a curl of sand sitting beside them like a little pile of spaghetti. None of these are the work of a bored child with a bucket. They're made by creatures living just beneath the surface, and once you know what to look for, they're one of the most interesting things on the beach to spot. This is a guide to what's actually making them, not a digging project — though a couple of these are genuinely fun to go looking for.
The coiled pile next to a small hole: lugworms
This is the single most common one, and almost everyone has seen it without knowing what it was. A lugworm lives in a U-shaped burrow just under the sand and feeds by swallowing sand from one end of the burrow, digesting anything edible out of it, and pushing the waste out the other end — which is what forms the distinctive coiled, spaghetti-like pile (called a 'cast') sitting on the surface. The small depression nearby, a short distance from the cast, is the burrow's other opening, where the worm draws sand and water down. Lugworm casts are extremely common on flat sandy beaches and tidal flats at low tide, and they're the classic sign that a beach's sand is genuinely alive underneath, even when nothing at all is visible on the surface.
The keyhole-shaped dimple: razor clams
A razor clam (also called a razor shell) lives vertically in the sand, siphon just below the surface, and leaves a distinctive keyhole or figure-eight shaped dimple where its siphon reaches up. This is the one with a well-known party trick: if you stamp firmly on the sand near a razor clam hole, the sudden pressure change makes the clam squirt a jet of water up out of its burrow — a genuinely fun thing to try with children, and the traditional (if not always successful) method some people use to catch them for bait or the table. Razor clam holes are most common on firm, flat sandy beaches, particularly lower down toward the low-tide line.
Small round holes with tiny sand pellets: cockles and other bivalves
Cockles and several other burrowing shellfish leave small, simple round holes, sometimes with tiny sand pellets scattered around the rim from their feeding and burrowing activity. These are generally less dramatic than lugworm casts or razor clam dimples and easy to miss, but they're extremely common on the same flat, sandy, tidal-flat stretches of beach.
'Bubbling' holes
If a hole appears to bubble or fizz gently as water moves over it — often noticed as the tide first comes back in over an area of exposed sand — this is usually trapped air being pushed out of a burrow (any of the creatures above) as water floods back into it, rather than anything alive doing the bubbling itself. It's a genuinely satisfying thing to watch for a minute or two as the tide turns.
How to tell natural holes from a half-finished dig
Natural burrow holes are small (generally under 2cm across), appear in scattered clusters rather than one obvious excavation, and are usually accompanied by other signs — a lugworm cast, a keyhole dimple, small pellets — rather than loose disturbed sand and spade marks. If you're looking at a single larger hole with a mound of freshly turned sand next to it, that one really was dug by a person.