When the builders constructed The River, the ceubaleia entered it to spawn, as if it were a bubble sea. Unfortunately, they were trapped by the gravity, and could not return to the air, try as they might. They could live in the river well enough, but their natural place is the free air, and they are prone to leap out of the water to try and find a way back.
Schools of immature ceubaleia swim the currents of the river, breaking the surface on their siphon jets, and gliding over the surface on their great pectoral fins, like flying fish or flying squid of earth, before slipping back once more into the River.
On the thin threads of the Loops, which swing up to the captive asteroids and back, the speed of the ceubaleia is enough to break them free, particularly in bends where the loop suddently changes direction. At that point, they can, with a mighty leap, break free of the lesser gravity of the loop and spring off into space. This is the source, too, of many bubble seas.
Ceubaleia are important food fish in their immature state, and are hunted as adults if they become stuck in the River. As for hunting the great adult ceubaleia who roam the zero gravity skies of the Necklace, that is a dangerous sport indeed! Collisions with these vast beasts have crumpled speeding airships many times, and even a glancing blow at speed can spell disaster.