it is an electric fence that lays
out over the water. Four strands. It is anchored to
the side with these black supports. Looking at the pond
it really blends in. It says it is battery operated, has all parts
in the kit, including energizer and can be expanded for
any size pond.

What happens when the wire falls in the water? I'd be scared
that the constant pulsing shock (electric fences cycle on
and off about once a second) would make the fish jump out of
the pond like they do when the water quality is bad. Maybe
the fish could avoid being shocked by moving to one side of
the pond, or maybe it wouldn't shock them at all or maybe it
would kill them outright (my garden e-fence killed a large
salamander once). I think it depends on too many factors to
be predictable.

The only way to know is to test it :-(