i would have to vote for a trackhoe being faster simply because you can load a dump truck faster than with a dragline. a long reach trackhoe would do wonders here it sounds like ,if there are any in your area. i would dam up a small area or dig a small area deeper for the fish then get as much water out of the pond as possible. digging through water can get things muddy all around the pond pretty quick.
unless you till bentonite in it dont work to good unless the leak is big and will carry the bentonite into the dam. i did see it mixed in a 80 bbl vacuum truck once and it worked on a seep. it was mixed at a low concentration and looked like milky water when it came out but it did work the owner also had several small water pumps recirculating the water and bentonite in the pond all day long. he was a retired drilling rig hand that looked like he knew what he was doing. i remember him saying if you just pour it in there it wont disperse enough to find the leaks and i also remember he waited until the pond was full to do this.
