 Within 36 seconds, he noticed. It's great that he noticed. We hoped that they would notice faster. He says in some cases, swimmers can submerge in just seconds, making them even more difficult to spot. It's time to reveal our experiment. There were four drownings that nobody spotted. What's that make you think? My kids were on the deck, so I turned my back. Doesn't mean there weren't other kids in the pool, though.