This is a good discussion topic!
I am planning on displaying my next build in a pier/dockside diorama. The model will be the MPM Type IIA, probably U-3 in a pre-war setting.
At this point I am considering my watermaking options, which as I see it are 3:
1) Embed the model in plaster, paint the plaster various hues of green with a little grey/green thrown in, then put in about 1.5-2.0 cm's of acrylic gel for surface texture, sheen and depth.
The advantages, IMHO, are the plaster is easy to paint, no heat or fumes to worry about, and it looks pretty convincing when done right. The main disadvantages are: I have never done it and plaster tends to shrink some if not mixed carefully.
2) Same as above, except very firm styrofoam is used instead of plaster.
Advantages are no shrinking to worry about and styrofoam is easy to work. The disadvantages are: Getting the styrofoam to fit the hull exactly (plaster would probably have to be used to fill any gaps), and I am not sure how well the styrofoam takes paint.
3) Cut the Hull lengthways to make it a waterline model, then use one of several techniques to simulate the water. I think the disadvantages outweigh the advantages with this option.
I plan to do test shots on both options 1 and 2 to see how they turn out.
What do you guys think?
Ernest