The water:
Most of the ship builders use some form of silicon for water bases, but I find it hard to work with and often produces unrealistic effects.
For this, I started by pouring plaster onto the wooden base. Getting the right amount is tricky, as you want it to cover the base but not run over the side. Shake the base to get it to spread out evenly and get air bubbles out.
When it is dry, dimple the surface with the dremel tool. This is messy!
Carve out the spot where the pontoon will sit.
I primed with an acrylic paint, then put on the blue color, which was enamel, but acrylic would be just as good. Overcoat with future to get it shiny.
Airbrush a lighter aqua color around where the wake will be.
I used light spackle compound to make the "foam" around the pontoons. Set the plane into the hole you made, on top of some spackle. Let the spackle ooze out the sides.
Then just do some dry brushing with white color to touch up.
It's really pretty simple.
Fred