I think the terminal velocity is about 150 km/h. Nowhere near the mach. The air slows you down within the first couple of seconds.
I ve done it in Wollongong, over the beach. It was awesome. I was screaming "F**K YEAH, YEAH!!!! THIS IS AWESOME!!!". The scariest part for me was the ascent in the plane, it was so small, tightly packed, with a little fiberglass door.... But it was worth it.