Why can’t I make a snorkel that is 10 feet long so I can breathe at the bottom of the swimming pool? — David, Raleigh, NC
Marshall Brain Answered:
If you’ve ever seen a normal snorkel you know it is about a foot long. And you don’t ever see snorkels longer than that. Like this:
Why can’t you make a snorkel that is longer than a foot? The problem has to do with the strength of your diaphragm muscle and the pressure of the water in the swimming pool.
If you look at the problem in reverse, you can understand it easily. People drink through straws all the time. But could you drink through a straw that is 10 feet tall? No. Your diaphragm muscle does not have enough strength to create that much suction.
When you get underwater, just a few feet of water is enough to put so much pressure around your chest that your diaphragm muscle cannot overcome it. You could try to make even a three foot long snorkel and it would not work. Your diaphragm muscle simply does not have the strength to inhale against the water pressure pressing on your chest.
It is interesting that elephants can snorkel in relatively deep water. The reason is because their lungs are completely unique among mammals. See this article for details: Snorkeling Elephants and the Secrets of Breathing
For more info on the bizarre world of underwater breathing see: How Scuba Works