I am an happily married man. One day I came home from work early and went upstairs to shower and change. I undressed and going to the bathroom I looked out of the window and in the garden I saw my 19 year old daughter sunbathing completely naked. She was lying on a lounger with her legs towards where I was looking. Her legs were apart so I could clearly see her vagina which was neatly trimmed. I did get an instant erection and seeing her like this really turned me on. I masturbated as I looked at her, at her exposed pussy. It wasn't long before I ejaculated. I did feel a bit guilty at having masturbated and cum looking at my naked daughter. When I think about it now I do feel some shame but I also get erect thinking about what I saw.