If you rent a water mouse, don't do it from DTD. Those boats are slower than the ones you rent at Poly or Contemp. They do this on purpose because of the layout of the waterways.
As for price, I believe water mouse rentals are about $25/30 minutes.
Great to know. This upcoming trip we'll be staying at Pop Century but our big trip next year, we'll likely be staying at our time share off site. I was hoping we'd still be able to rent boats from the Poly as that is my favorite place I've rented from. I don't know why, I just liked renting them more when I stayed there a few years ago.