For centuries, an uncharted island off the coast of Hoenn was known only for the large population of Carvanha which sunk any ships which ventured too near. It was marked on maps as "Savage Island", and the name was thought to derive from the fact that it was a land where the savagery of the wilderness could survive, untouched by man. It was not until the past two centuries, when boats began to be made of materials too strong for Carvanha's jaws, that it was learned that this respite of "savagery" possessed its own civilization, and that each and every member of the enormous Carvanha armada surrounding the island was domestic!
It was not long after that the truth of the island's history came out, although it required no shortage of lives and courage to be learned. The island's people were themselves thought of as savage, a term which in this case meant little more than "different" and "technologically backwards." They had long possessed a custom of training Carvanha for protection, which was looked down upon, for they were a hated pokemon by outsiders. Disease and slave raids had gradually caused their population to dwindle, and knowing no other defense and seeing nothing to gain from the outside world, they had voted to seal the island off, planted tall trees to shield themselves from the air, and pooled their pet Carvanha into a massive navy to protect themselves from outsiders.
Thus they had survived unharmed for centuries, protected by a vast fleet of pokemon which sink ships, drink blood, and have a reputation far more fearsome than their tiny size justifies.