We just completed our most recent pond. It is 5000 gallons and we have three labs and a shepard mix. Two of the labs used to get in the pond in NM but don't try this one since the sides go straight down with no shelf of any kind. One of them slipped in the shallow end and was able to get out but the deep end (4ft) is too deep. There is a bridge across the deep and shallow without enough room to swim under. We were worried about them not being able to get out if they fell in, so we put a milk crate for a step. I can see that something (probably a raccoon) has been on the crate so we moved a bunch of floating plants over it to see it that will stop it. I don't care how much of a mess the dogs make getting out if they accidentally fall in as long as they don't drown. Our big white lab makes every diligent effort to see the fish. Some times she is rewarded with a glimmer but she never gets in this pond. She, along with our big black lab are the ones that used to get in the pond all the time but never here. We have one who only wants to follow the fish food floating and gingerly stretch to grab as much as she can. Our liner in NM where the girls used to get in was 45 mil and we never had a problem. I don't mind much if the girls get in as long as they can get out.