Why use a pond when they had a big old ocean right there and a side of the island where bodies would go out. And boats. I don't get this myself.
because on that side of the island a body would wash up. Plus the first thing people will think is that they did dump her in the ocean. It is easier to weigh her down and sink her into a water hole somewhere. Remember they really did not have a lot of time and where probably panicking. All this would fit if they were there at the club and kept coming back to it. They may have been sitting in the car after the dirty deed coming up with their alibi's and story when they were seen.
Also they may have dumped evidence in the pond.
Oh this Nancy Grace is just gross... but Joran has told 22 (TWENTY TWO) different versions of what happened that night.