My father almost drowned once, he said it was almost peaceful. He didn't really get sucked under violently or anything though, he was deep sea scuba diving and had a malfunction with his tank. Was trying to get to the surface and passed out about 20 feet below the surface, but he ended up floating near enough to the surface when his buddies in the boat saw him and dragged him back up. Still though, I was shocked to hear him say it was peaceful for him. I would be panicking like hell.