Action films and cartoons share a common idea, well, many ideas, but I will call your attention to this familiar situation.
Our hero be he Bugs Bunny evading Elmer Fudd or a warrior on the run encounters a river. To thwart pursuers, he plucks a reed from the surrounding vegetation and submerges himself with only the reed protruding above the surface. He remains stealthily submerged until the pursuers have passed.
There are also more than a few accounts in legend of various feats of escape that utilized this same breathing-though-a-reed trick.
Our surface interpretation of this feat is that it is plausible, after all, the reed is operating as a snorkel and snorkels do a fine job of allowing one to breath while submerged.
But, let’s look at the bare-bones physics behind this.
First-The deeper we submerge the pressure change prohibits us from being able to breathe non-pressurized air—scuba tanks contain pressurized air. When we use a reed, we are attempting to draw directly from the atmosphere, a non-pressurized source. The external pressure on the chest makes it harder to draw [produce the suction] for a substantial breath.
At a depth of a mere one meter it is no longer physically possible to take that reed breath. And this holds for strong-lunged individuals and weak-lunged individuals alike. Most people find drawing a breath at even half that depth is quite difficult.
Second-The air in the reed must be exchanged. As we increase the length of the reed we increase the difficulty of gas-exchange. We add to this the accompanying friction for every bit of length gain increasing our difficulty of draw which is already compounded by the external depth pressure.
Third-Reed diameter. Compare the experience of breathing through a narrow aperture such as a drinking straw and that of breathing through a snorkel. The snorkel’s aperture is far easier on the draw.
But…there’s the snorkel idea again.
Is not a snorkel essentially an artificial reed?
Only in appearance.
Snorkel design takes in the above physical deficits.
One-They have wide apertures for ease of draw.
Two-The have short length to ease gas exchange.
Three-The short length is also to compensate for the known pressure problem. Snorkels are designed to be used while you are face-down in water, essentially skimming along the surface not actually submerged. We see no extra-long snorkels because the designers know of the physical limitations [both biological and mechanical limitations] that would render the product dangerous.
With the above in mind, we can enjoy our cartoons and if ever evading pursuers in water skip the reed. It is wiser to work your combat breath-holding, your “splashless” swimming tactics, and the whole inventory of aquatic stealth.[For more Old School training practices subscribe to this blog, the RAW Subscription Service and our upcoming book Rough & Tumble Conditioning.]