well, even though it's not really a shader, do you gurus know what is meant here when they speak of a "gerstner wave function"?

http://www.futuremark.com/products/3dmark06/tests/

i'm currently learning hlsl (proceeding well so far) but this is a thing which i've never heard before. i can only find essays and papers about physics and fluid simulation but nothing that tells me wether it is a shader or applies just to geometry transformations.

thanks in advance,
joey.