After Maya’s Ocean test, I use the latest release of Blender (2.72 RC1) for the ocean modifier.
Using the same boat, it’s much easier to use the depth of field in Blender with the combination of empty locator attached to the boat; the camera’s depth of field focus to the empty locator, and the defocus node in compositing. I use Blender Internal for rendering.
My boat is much faster than the speed boat. :p