Is it part of the cord that is submersed, or the part that is kept external
to the pond? If so ( not submersed), repair the wiring and seal it in
silicone. If it the submersable part, I wouldn't do that though. The
reason I say silicone is, that is what the phone company uses to seal up
broken or cut phone lines, yep that is experience talking. They repair the
wires and stick the repaired part in a little black box full of silicone and
close the box and you stick it back in the ground. I would go get a hobby
box and fill it full of silcone,cut holes just big enough for the cord stcik
the repaired part in there, if you keep the repair small you could even use
a medicine bottle. Someone else may have better ideas that me
though....Claude