I'm modeling light interaction/reflection from a fiberglass surface with polyurathane epoxy (that is very reflective) that has been spray painted with a matte black paint. I'm looking for some input - is it reasonable to approximate this as specular reflection from the polyurathane with a loss factor from the paint absorption? Is there a better way?

By way of context, this is a large water tank where we do experiments with underwater optical communication. I'm building a Monte Carlo-type simulation to match our experimental outputs. The wall surface reflections are giving me issues.

I'm modeling light interaction/reflection from a fiberglass surface with polyurethane epoxy (that is very reflective) that has been spray painted with a matte black paint. I'm looking for some input - is it reasonable to approximate this as specular reflection from the polyurethane with a loss factor from the paint absorption? Is there a better way?

By way of context, this is a large water tank where we do experiments with underwater optical communication. I'm building a Monte Carlo-type simulation to match our experimental outputs. The wall surface reflections are giving me issues.