I agree about the impressions point. High CTR or not, the Ad is indeed shown to the user, and to look it form a totally different PoV, the low CTR ads mean relatively low CPMs (i.e. eCPM, assuming CPC to be low). If looked from a pure branding or impression perspective, this might be desirable (although I'm not saying low CTR is good for the publisher OR the advertiser).
Well, I had almost drowned once. I had a personal flotation device and I knew swimming! We were out rafting, and I had swayed away from the raft swimming in light rapids (the instructor said its very safe - which it wasn't). When I realized that the rapids were overwhelming me, I tried to stay afloat (a flotation device and know-how of floating works - but I guess I was panicked!), but did not help too much. It took me sometime to realize I was drowning, and in the meantime I had told another raft that had approached to help - that I was fine (overconfidence?). When the reality hit, it was bad, and I could not even scream. I did wave my hands, on to which my friends on the raft threw a rope, and I survived.
Even swimmers (I consider myself below average) can drown. "Panic" is to blame here. The following article explains a similar case quite here (search for "scuba-diving"):
