How to super-impose something into this scene?

[Luca31516129jfxi]

Hi all,

I'm trying to super-impose something into the river in this clip and make it look like its "behind" the railings. I've tried rotoscoping everything that isn't water and putting that on top but the results have been quite poor. Any other ideas?

[Rick Gerard]

I would approach the problem by trying to use Keylignt to create a combined matte for the water, add a Black Solid to mask out everything not on the water, and then start combining things to generate a Luma Matte for the layer you want to place on the water. Add a Displacement map and maybe some blend modes to the object on the water, make it a 3D layer, and animate its position, and you're pretty close. The idea is to get as much of the matte created as possible using procedures (effects) to eliminate most of the keyframes and roto you need to do.

I got this in about 10 minutes:

I included the project file for you to look at.