The Dolphins of Pern (Dragonriders of Pern)

Used - Two boys, one of them a dragonrider, re-establish crucial contact with the wise dolphins, the legendary "shipfish" of Pern.

When the first humans came to settle the planet Pern, they did not come alone: intelligence-enhanced dolphins also crossed the stars to colonize Pern's oceans while their human partners settled the vast continents. But then disaster struck.