The beach at Platamonas hummed with activity. It was Saturday morning, and the beautiful stretch of white sand along the Greek coast was full of people. Some were locals enjoying the weekend. Others were tourists staying at the various hotels that studded the resort town. Already a firm favourite with Russian, Bulgarian and German visitors, it had recently been discovered by the British and the first coachloads of British tourists had arrived the previous day, swelling the numbers already in residence. Now the beach was crammed with people, dogs, sunloungers and bags. Pale, pasty-skinned bodies waded off the shore. Some brave souls dared to swim, and before long the water was almost as crowded as the land. A buzz of noise spread from one end of the beach to the other.

The noise of the revellers spread beyond the water’s edge. Further out to sea, past the range of the swimmers, it disturbed the lone denizen of a grotto deep beneath the waves. The noise of hundreds of beachgoers reverberated off the green and blue coral walls of the undersea cavern, echoing through the submerged chamber. That lone denizen stiffened in annoyance. A forked tongue flickered. Claws unsheathed and sheathed again in irritation. The water rippled through the grotto as a scaly tail thrashed.

No-one was sure, later, which of the several boom boxes brought to the beach by tourists was switched on first. The locals insisted they had brought no such thing. It would be rude, they asserted, to drown out everyone else with their own music. If any of the old grandmothers and grandfathers recalled the stories and traditions of their childhood, the real reason why such devices were never brought to this particular beach, they did not share them with outsiders. But the foreigners switched their boom boxes on, and loud music erupted from several spots in the crowd, becoming a raucous din of competing sound.

The racket was not confined to the beach. It rolled out to sea. The cacophony transmitted across open water and into the depths, losing none of its volume. In the deep sea grotto, claws flexed. A scaly tail thrashed again. And a decision was made.

The incredible din meant that the first panicked yells and screams of tourists in the water went unnoticed. But it did not take long before people saw the huge ripples bursting against the shore, far too large to be normal waves, and beheld swimmers, those who had ventured furthest from land, picked up by tornado-like spouts of water and flung through the air to splash down in the shallows.

Most people gaped in shock when the scaly tail, longer than a bus and tapering to a point, broke the surface and slapped the water hard, generating enormous waves that sped the remaining swimmers back to shore. Others turned and fled, screaming at the top of their lungs as they escaped the scene.

A scaly green neck erupted from the water, topped by a head the size of a small car. Huge teeth gleamed in the sunlight as the monster opened its jaws. Vast amber eyes glared balefully at those humans who had not yet fled. The beast sucked in a deep breath and then exhaled. An enormous jet of water shot from its maw, like a high-pressure water cannon but super-sized, mowing down the remaining bystanders. Drenched, terrified, they scrambled to their feet and fled the scene. Their dogs, barking wildly, led the way inland. In moments, the beach was cleared.

After several loud crashes, silence reigned on the now-empty beach.

Those brave souls who dared return, some hours later, reported that all of the belongings abandoned on the beach during their rout remained intact. Except for the boom boxes, each of which had been smashed to fragments. Remarkably, no-one had been hurt, at least beyond minor scrapes and bruises.

The eldest among the locals murmured knowingly to one another. They knew the stories. They knew the old ones would only cause true harm as a last resort.

Deep in his undersea grotto, the sea dragon embraced the renewed quiet, the raucous din of the hated noise machines gone. Satisfied, he curled up and resumed reading his book.