Somehow, cowboys are able to do damage to repguanas in the Repguana Sanction when the cowboy is underwater and shooting into the wall. I'm not sure the specifics... but I've seen it happen a few times. This is NOT just shooting upward - that would be "legit".
Also, I have manual enemy control. But I can't force the repguanas to fall into the water. Being able to do this would effectively solve the above problem.