Black tarp-like material under the front part. What is that?

^I agree, that is a water barrier, that likely covers the entire floor. It probably has a thin fiber insulation, to keep the floor warmer.

I also noticed the common thin straps holding the fresh water tank up. They appear to be rusting at the bend (also common), and don't offer much support, even when new. You should be able to fill fresh tank, before travel, and not worry about it falling out on the highway. I'd add, bolt on, a more solid support.

Jerry