The fish...
...are modeled with Symmertrical Lattices (Sym Lats)
so a Terrain was made like this
(it's inverted so you can see the faint gray fins,
& squeezed to take more advantage of the square terrain shape)
The Terrain -------->
----

for a Material surface the fish needs 3 maps
Color Map
from a fish book
A Transparency Map
A Bump Map
This fabulous idea for making a fish in Bryce came from Sandy Birkholz who sent me the trout color map. I spruced it up and added the bump and transparency maps.

But how about that bentfish?