Back in high school, I used to spend almost every summer day at the lake with all my buddies. One day, one of the guys said, “Hey, race you to the other side of the lake” and 4 of us jumped in and went for it. When 3 of us reached the other side -maybe 200-250 yards away - and jumped out laughing and pushing one another - it was time to notice that A. was gasping and struggling for breath in the middle of the lake. We jumped back in and floated him back to the other side, and when he was talking again, I asked him, “What possessed you to try to race a bunch of swim team members when you obviously can’t swim and we’d be back in 20 minutes anyway?” He never came up with a satisfactory answer, but I guess he felt left out. There was no alcohol or undertow involved.
After that, we got a little more careful about “Hey Tim, I’ll race you to the other side.”
There is a great discussion on how close folks have come to drowning.
I explain in post 36 my SCUBA experience on my second “post certification” dive.
I am a VERY strong swimmer, and I’m pretty much on board with Critical1 's assessment of a swimming experience. I plan to teach the same things to my daughter when she’s ready for swimming lessons (she’s 5.5 months now, a bit early yet…)
As long as you know what you’re doing, it’s fairly safe… but if things go wrong, they go wrong VERY fast.
-butler
I had a friend who almost drowned in a gravel pit one summer. He was drinking, and the cold water quickly made him want to get out. He swam to the shore, but was at the opposite side from where he entered. The bank was steep and he could not get out. If he were sober he would have just swam to the other side and emerged easily. Instead, he struggled until exhausted and only at the last minute thought to swim to another area of shorline. He pulled himself out and lay gasping on the beach. That was when I arrived and heard his story. He was very drunk and very blue.
My husband’s uncle, an avid boatsman and by all accounts a strong swimmer, drowned last summer during a vacation on his boat. He was alone at the time, so no witnesses to what happened, but we know he had a pretty severe case of Meniere’s disease, a disorder of the inner ear. Best reconstruction is that he went on deck after his wife had fallen asleep - maybe to get some fresh air, maybe to investigate a noise - had a serious vertigo attack, and fell into the cold water.
I’ll admit it made me angry when the newspapers mentioned the drowning but failed to mention the Meniere’s disease - you could easily come away with the assumption that he had killed himself or had been drinking. He was not a likely candidate for suicide, and the autopsy showed no sign of alcohol. The only dumb thing he did that night was go up on deck alone without his life vest, knowing he was subject to severe dizzy spells. Unfortunately it was the last dumb thing he ever did 
Unfortunately, though, the statistics I’ve seen for drownings in Norway, a coastal nation with a great love of small boats and days spent at the beach, show that particularly younger adults who drown or nearly drown are frequently under the influence at the time. Others fall out of boats without adequate life vests, and either overestimate their ability to swim, or are injured in the fall and are unable to save themselves.
Heh…I almost drown at a swim meet…and I remember at the time thinking…Hmmm…there are lots of timers and officials and coaches and parents watching me not breathing out here, but there is no one in the lifeguard chair. I had a mental meltdown and inhaled before my mouth cleared the water level, about 20 yards from the finish in a 50 yard pool (the damn middle of the pool). I can still remember (like 15 years later) the looks of horror on people’s faces. They could plainly see I couldn’t breathe and wasn’t handling floating and swimming too well, but nobody had the responsibility to come in and help me. I finally made it to the end of the pool and my timers pulled me out since I was too weak to lift myself. The officials were nice enough to not disqualify me for breaking stroke symmetry.
I have also gotten way to tired and cold in rivers and lakes. Moving in water is much harder than moving in air and cold water chills you much faster than air. Now I am older and smarter and wear a life jacket and a wetsuit when I am on or in lakes.