It's not a matmatics shader, I think,  but Fisty posted liquid shadeers for DAZ's 24 days of Christmas:

http://forum.daz3d.com/viewtopic.php?t=178340&flatnum=1

and a preview is here: http://forum.daz3d.com/postimages/origimage_1_3192045.jpg

Maybe you could use those as a base?