I've made several small updates, the big ones required a significant amount of 'dark work'.
(1) A custom water shader which feels like a big upgrade coming from a standard blue shader with alpha. The shader distorts textures behind it according to a noise map and also creates a nice blue/green color gradient.
(2) I've added a simple propulsion method with a mediocre model/animation, I plan to upgrade all the models as I'll be shifting to art soon.
(3) A realistic drag model (air and water) which takes into account the rendered water surface height, angle of the objects surface to the water and the relative velocity. Drag is calculated in all directions.
The result of these 3 elements can be seen in the gif below. I've noticed that the addition of the drag physics really forces you to create actual boat shaped hulls. Before when I was testing, some pretty silly designs were super effective.
Water shader available here