Leaking coolant from transmission

Hey everyone! Yesterday my vehicle began running really hot. I pulled over and found it was low on coolant. A guy at the gas station put some water in it, and I got it to my Dad's house. He and his friend looked at it and they found water leaking from a perfectly round hole that is about a 1/4" in size. They said the hole is on the driver's side and on the metal part, not the plastic. Dad had to loosen the sheathing to see it. He can see where the drain plug is, so it is not that. Also, when I tried to Google some information last night on it I thought it might be the hole for the water pump tp "weep" out of, but it seems those are generally near the water pump, and this is not. Any ideas? Thank you!