Mike Patterson wrote:

Landmines, works every time ;-)

Effective, but could bother the neighbors, and the police might frown
on it.

I'd suggest a wire around the top of the fence that was climbed,
hooked to an electric fence transformer. Just to keep the birds from
fouling the top of the fence, of course.

If the neighbors object to that, they can't do much about you running an
electric fence around the pond, to keep out the raccoons.
--
derek