Pigs walking around on the pond banks are theoretically supposed to compact the soil similar to a sheepsfoot roller. Very lucky the pondowner if this technique works. Shallow surface compaction from pigs will probably not work because there are too many variables or other reasons why the pond could be leaking.

If this technique reliably worked it would be in wide-spread use today. You are dealing with folklore.

If the pigs do not work at least you know the problem is deeper within the ponds banks than the surface layer.

aka Pond Doctor & Dr. Perca Read Pond Boss Magazine -
America's Journal of Pond Management