Jason, where is your coop in relation to the pond? Can you not entice them into the coop [food/treats] late in the day and then keep them safely there overnight?
We have nesting boxes [drawers out of an old chest and a slatted crate with one top slat removed] in the female coop -- they use them all for napping in but will only lay in the slatted crate. Muscovy and pekins are the same in that regard and one of the pekins keeps all the eggs warm until I got to pick them up. I don't let them out until they have done laying for the day as last year, we had the crazy egg hunt every morning as one of the pekins
Otherwise, out in the wild by a pond, they will lay where they fancy and that might be a different place each day.