I’m modelling a harbor/waterfront and am seeking advice on making a realistic looking harbor. Research indicates that both of the above-named products seem to be designed for this sort of application. How deep a layer should I install for a convincing look? And also, should things like pier pilings and other structures that would normally contact the water be installed before the “water” is poured? The surface area is about 4 square feet. Realistic Water seems to be easier to work with - is one product superior to the other? Any insight would be appreciated.
The pilings should be in place when the material is poured. Either product should be a thin layer. If you need more depth, allow the previous layer to thoroughly dry and then pour another thin layer.
Envirotex will creep up the pilings and embankments, and there’s no way to stop it. Realistic water may do the same. With either product, your base must be thoroughly sealed or it will all leak out through the slightest opening.
For large harbors, I prefer to use the plastic used in door windows,(with a tiny random pattern of raised relief). I scribed the flat backside, and snapped the sections as needed. I painted the flat side with dark blueish-green similar to the color of harbor water.Bob Hahn 
I use Envirotex for all my water.
Hint: Go to www.michaels.com or www.acmoore.com and find their coupons. Each of these craft stores usually has 1 coupon good for 40% off one item. That’s real money if you’re buying Envirotex.
The trick with water is to get the illusion of depth without actually making something deep. My deepest water is no more than a half-inch, yet it looks much deeper. The first step is to paint the floor of the harbor in dark colors - black, dark green, dark blue, brown. As you get to the edge, taper off the dark colors and use lighter ones.
I like to use about 3 or 4 pours of Envirotex. I tint the lower layers with a bit of craft paint, just a drop or two. This gives the Envirotex a slightly murky look, and greatly adds to the illusion of depth. This is after 1 or 2 layers of Envirotex. Since you asked, there are pilings for the deck of a waterfront restaurant that the water is “flowing” around.
I use pink foam as my layout base, and I usually cover over water areas with plaster cloth, after gouging out the foam to get a sunken area with an irregular surface. I concentrate on painting the deeper parts black. Once the first layer of tinted Envirotex is poured, they are already become “deep” from the dark color and the unclear water. On subsequent layers, I use ligher tints, and I usually don’t tint the top layer at all.
The finished harbor looks deep, but it isn’t.
For me, I like Envirotex. Realistic Water tends to yellow over time. They both tend to creep up pilings, rocks and sea walls, but after it has cured you can always use Testers Dull Coat. Spray some in a little cup and brush it over everywhere it has crept up to. For salt water I like to paint my base a very dark blue, almost black. My harbor is 1/4" deep, and done with two pores 
wops, Sorry about the type-O That would be two pours.