Jan de Boer wrote:. . . swims . . . cramp . . . if this would have happened in the middle of the pool, he could have drowned. It probably is not even that uncommon.
There is standard teaching that eating before swimming causes cramp and cramp will cause you to drown. I am quite sure that is false. Even if cramp causes you to stop swimming in the middle of the pool, you should be able to stay afloat long enough to pull the offending muscle and relieve the cramp. And I am sure that eating isn't the cause of muscle cramps.
Now, swimming after drinking any significant amount, that is different. You can go straight to the bottom and stay there. Don't drink and fall off the quay into the harbour. Another thing is going suddenly into cold water, particularly when the air is warm. The sudden cold can interfere with normal breathing for up to 30″ and that is long enough to drown you.