The Trench

About a half-mile out from the black-sand shores of the Western Ocean, the floor of the sea drops down into an impossibly deep trench. To go all the way down would mean death from too much water pressure for dragon and rider alike. The further down you go, the more glowing fish there are. Just be careful of the giant squids that tend to roam around down here, and the mythical pathoshark that would eat any creature alive.