I remember reading this story some time ago. It was an AU and John and Rodney were both in their teens.
From what I remember Earth was under attack and certain people on the planet were beamed aboard a ship and taken to Atlantis. Rodney was taken and was given about five minutes warning to grab some stuff, I think he had been pre-chosen because of his genius, he took a very young Jeannie with him. John was one of the other people but he thought they may had taken him instead of his father as his father was military. On the first day John dived into the sea to rescue someone who they thought was committing suicide.
Found: Twilight of the Fifth Sun by tzzz
From what I remember Earth was under attack and certain people on the planet were beamed aboard a ship and taken to Atlantis. Rodney was taken and was given about five minutes warning to grab some stuff, I think he had been pre-chosen because of his genius, he took a very young Jeannie with him. John was one of the other people but he thought they may had taken him instead of his father as his father was military. On the first day John dived into the sea to rescue someone who they thought was committing suicide.
Found: Twilight of the Fifth Sun by tzzz