mike,you are 100% write.i know of it being done several times.my neighbor's papa has done it several times for cattle ponds.i can remember as a young kid asking him what the pigs were in the hole for.i just called my neigbor and he said he did not know the details of it but he could remember there were quite a few pigs and he kept them in there for what he thought was about 4-5 months.
