Water effects question.

Terrain day is coming up, and even though I don't think I will get around to it during the day, I figured I would go ahead and post it.

We will be making our terrain on pink foam, and 2x2feet squares. The foam will be 2 inches deep, and we will make different levels of the city by stacking foam.

Now, around to my question. Since the foam is rather shallow, I am having an issue with what I want to do. I want to make a port, and because of the 2 inch thick foam, I'm not sure how to get the 'really deep and dark water' effect. I am also not sure as to what modeling water solution I should use.

Any suggestions would be greatly appreciated!

Oh, and there will be lots of trash in the water, littered and polluted, so it will be dirty. Any suggestions for gunk floating on the water? Like mold?

Simples solution is to paint the foam a darker colour in the deeper sections, or mix in darker inks with the water effectes to create the illusion of deep water.
I.e. mixing a dark blue/green ink with the water effects, slowly watering it down and lightening the tint as it gets closer to shore...

Thanks for the info!