This story was related to me by a friend.
About 5 years ago my best friends sister (Sara) and her husband (Mike) bought a house. It was a decent house. It was a single story 2 bedroom with a big backyard. In their livingroom you can access the back yard via a large patio with a sliding glass door that had blinds for curtains. They lived there about 2 months and decided to have a house warming party. The night of the party several of the guests were in the livingroom. Sara's brother was standing by the patio door when he suddenly heard a knock on the door, thinking it was someone outside smoking he opened the door to let them in but as he did, he saw that no one was there. At that time he just dismissed it and told no one.
About 2 weeks later both Sara and Mike were in the livingroom watching TV when they both heard a knock on the patio door. This kinda freaked them out seeing as how they were the only ones there. Mike got up and opened the blinds thinking it might be an animal or something but when he did nothing was there, they both decided to say it was some sort of settling of the house so they left it alone.
Over the next 3 months they had several incidents where they heard the knocking on the patio door and Mike thought it would be a good idea to leave the blinds open to see if maybe it was a prank or something done by the neighbors. So one night again they were watching TV, when Mike looked up and got a sudden look of terror on his face, there at the door was a little boy. He was wet and wearing swim trunks. He started knocking on the door and had a smile on his face. Mike rushed up to let the boy in not wanting him out there cold and wet (it was winter) but as he got up the boy vanished. Both Sara and Mike had enough and they decided to start looking for another house.
Not much happened for a bout 2 months after that.They found a new house and were in the process of moving when one night they were packing up the livingroom (they stopped staying in that room and was the last room to pack) when Sara looked outside on the patio. What she saw she'll never forget.
The boy they saw 2 months prior appeared to be coming out of the ground, as if he were getting out of a pool. As soon as he got up he sort of trotted towards the patio door, knocked then disappeared. Sara was very scared but pretty fascinated about the whole thing and after they moved she looked in to the history of the house .
According to the old owner, there used to be a swimming pool in the backyard and the family before that had a son about 10 who had drowned in it, the parents were so upset that they had the pool filled in so it wouldn't remind them of the accident.
Thats my story thanks for reading.