A-ha
glad I found this as I was toying with getting a couple of ducks as hopefully a solution to my slug and snail problem.
I have an old Eglu that my hens outgrew, and I have a fenced-in veg plot (to keep out deer and hens) that they'd live in. There's room for a small pond if I shuffle the compost heaps around a bit.

Do you reckon that would work ? Won't they fly away ?