The first pond (the one I need done this year, future ponds will come in future years) is going to be a rectangle, 16'x8', the deep end will be along one of the 16' sides. This pond is half the area of a 16x16 pen.
The deep side will be a 16' long trench down to at least 3 feet, then slope up slowly to ground level across the 8' width of the pond. The trench deep spot will have a few inches of sand in it, so any water turbulence in the pond would move stray sand back to the trench and I can keep my filter pumps away from there.
I'm going to use a standard 45 mil liner, but I need to find some places to order them cheaply (that and pumps).
I've thought of the tiller. I have a neighbor that might loan me his, but I have these HUGE rocks in my yard, all over (literally, I've pulled over a dozen boulders I can hardly lift out of the trenching I've done already) and I'm not sure if it's safe for the tiller to run it in that rocky of soil. I'd feel like a schmuck if I busted my neighbors equipment.