FineScale did some articles on the topic:
Feb 1984 pg 60- Modeling water with artist's acrylic gel
Jun 1987 pg 34- Modeling water from above and below
May 1990 pg 50 - Modeling water with plastic resins
Sep 1996 pg 38 - Craft store clay (Sculpey) is ideal for water
Dec 1996 pg 66 - Making bow waves with paint