Next week I'll be at a large Adirondack lake. At one particular spot, a
stream dumps over a 50' ledge into this lake, so there's perhaps an acre of
water that's cooler than the surrounding area, and I've caught the
occasional rainbow there using Mepps spinners or similar things. This year,
I'd like to try the spot with a fly rod. The water's pretty turbulent for
about 50 feet around the falls, so if trout are surface feeding, I've never
been able to see it. What sorts of flies would be a good starting point for
experimenting in a spot like this?

I'd prefer something that is 100% resistant to wind knots.