The name of the seaside village varies from telling to telling, as does that of the hero, and the identity of the dragon pokemon involved. In Kanto, it is a Dragonite, in Hoenn, a Salamence, in Sinnoh, a Garchomp; the story is unknown in Johto, perhaps because there was no dragon which it could be transposed to.
In all variants of the tale, the dragon is portrayed as a horrible tyrant. The people of the village are too frightened to lift a finger, and a young trainer with only a Cloyster which can not beat even the village children in a pokemon battle is the only one with the courage to fight back. He takes a ship to the dragon's lair, or surfs across on the back of his pokemon, and deep in the local cave he confronts the dragon. In some variants, he holds a spear of ice given to him by his Cloyster, in others, he orders the Cloyster to use the attack "Icicle Spear". In reality, he fought alongside his pokemon, hurling spears into the dragon's eyes and slaying it in a sextuple shot.
In the villages once terrorized (for there are many which claim to be the source of the legend), celebrations still take place on the day of the dragon's death, centered around a ceremonial "slaying" of the dragon by a Cloyster. In reality, it is a knocking out, although in the old days the dragon's wild descendants were captured and slain for the festival. Interestingly, with the increasing dominance of dragon types, a few trainers from these villages have brought the ceremony to the Pokemon League, against dragons not instructed to throw the match: they have typically succeeded with Cloyster, but been let down by its teammates.