Have not run many bullets into water since my days of a being a commercial loader/reloader back in the 1980s. Decided to put a catch bod together and see what some of the rounds available today do when run into water...
Catch box is 4' long and will take 8 one gallon plastic milk jugs. Most HP bullets never make it beyond the third jug. Some harcast will make it through all 8. I also learned that plastic sometimes is too tough especially for the initial expansion and when possible use paper cartons instead. One 1/2 gallon paper carton equals 1-1.5" of ballistic gelatin... but collecting paper cartons is a pain and it takes a LOT of then to do a lot of testing...so I compromised by using one paper carton backed up by four gallon plastic jugs and then an out of date soft body armor panel to stop anything going beyond three jugs...
..and a chronograph 10' from the muzzle, the first carton 21' from the muzzle.
Bob