I lent my windsurfer to an elder in the 1990's, I must have been about 21. I was watching as he had an epileptic fit and fell off the board, sinking to the bottom of the lake where we were. Luckily he was only a few meters from shore at the time and the water was only about 1 meter deep. I ran in and pulled him out, surprised at how heavy he was, he was like a stone on the bottom. It really shook me up, as the lake is very deep and if it had happened when he was further out I would never have been able to reach him.
It affected our friendship, as he felt very embarrassed about it and never the same around me. He also never thanked me, but a few weeks later he called me asked that I not judge him, as I must think that if the same thing happened when he is driving he could kill someone. I had not even thought about that before he brought it up.