Remember to brush your fish.

I made a fish brush for the Bryce 6 Terrain editor. It's a .png file. Download it and then open the brush window in the terrain editor. Click "Add" then locate the png file.

In the working window, just click once for each fish. Clip the bottom of the terrain off and make it very thin in the scene. You could probably add a darker dot for an eye on each fish, or do it in postwork. Best for a distant school of fish