Just today my father in law and a friend of his were fishing a local lake, when they heard a scream for help. They quickly fired up the motor and rounded the bend to find a man struggling to stay above water. They managed to get him into their boat and back to shore. He was fishing in a small aluminum boat when it began taking on water. He had a life jacket in the boat but was not wearing it. I guess he couldn't get to it when the boat was sinking.
Besides the obvious safety ideas, I think everyone should take some type of swimming class.. even if all you do is learn to doggie paddle. This guy did not know how to swim at all.