The pond had accumulated a LOT of leaves over the years and hadn't been cleaned out since we-don't-know-when. So it was time just deal with it already. Having a heavy-duty water pump was really helpful and got the water out pretty fast. With an extra long hose, we just drained it into different areas of the yard.
Towards the bottom, I switched to the shop vac since there was no water left, only really thick muck. The pond has been refilled and the frogs are happy.