Rick is correct, Louganis did hit his head on the springboard in Seoul. The added drama was that, at the time, Louganis knew he was HIV positive, but he hadn't disclosed that or come out of the closet. He was then very fearful other competitors might contract HIV from his blood in the water.
The story I heard was he privately told one of the USA swimming & diving doctors, who thought that a tablespoon of blood in a chlorinated pool wasn't a danger to anyone. Given that everyone now know and no diver has stepped forward to claim he or she now has HIV, the doctor seems to have been correct.
I'm an Olympivs junkie.