Patching A Tub....Help!

Submitted to Community Café

I need some good advise. I am in the process of refinishing one of those resin tile shower/tub surrounds. Before I start on it, I need to patch a small size of (size quarter), a small area on the floor of the tub. What can I use to patch this??? Does anyone know what I can use???

The pic below....wow! looks like it's foaming....but same as pic above.