I really enjoyed this post by Will O'Brien on Divester. Divester is beginning a new series on Scuba Diving Theory starting with this fantastic article. There are some good reader comments posted on this page as well.

Quoted from Divester: We're beginning a series on SCUBA diving theory. Not only will we explore techniques and best practices in safety, we'll talk about the reasons behind them. Bad puns will abound as we dive into everything from using and maintaining your gear to compartmental decompression theory. Today, snorkels: they aren't evil.

Do you carry a snorkel on your dives?
I've met several divers lately who leave the snorkel at home when they go SCUBA diving. The snorkel has become percieved as dead weight that tugs at the mask strap. Today I'll talk about the importance of strapping that tube to your head.

Snorkels are annoying
They add extra drag to your head. They poke you in the chin. You forgot the one that isn't pink...
Yup, they're just obnoxious, until you need them.

I'm diving, not snorkeling
According to reports by DAN(The Divers Alert Network), the majority of diving deaths at the surface in 2005 were due to exhaustion. In one case a diver drowned at the surface after he dropped his regulator because his tank was empty at the beginning of his dive.

That boy's head is like Sputnik
In full diving kit, keeping your head above water is very exhausting. The human head averages about 12 pounds. That's a big weight to keep out of the water. Oh, and don't forget that the top of the tank and your regulator are poking out of the water. Lets make that 20 to 25 pounds of dead weight. Inflating your BC will offset the weight of your noggin, but todays BCs are not designed to keep the divers head out of water.

Please sir, make them smaller
It's not entirely the diver's fault that snorkels are being left behind. It has become difficult to find a simple, streamlined snorkel in a dive shop. Purge valves certainly make clearing a snorkel very easy. Unfortunately adding a purge valve makes the snorkel bigger and heavier, resulting in more drag on the divers head. My favorite, trusty, valve free SCUBAPRO snorkel isn't even made anymore. Purge valves are simple devices, but they can fail. A piece of sand in the right place can turn that spiffy valve into a water inlet. Aside from children's gear, my local dive shop doesn't even carry a snorkel without a purge valve.

You're still not convinced?
For the local Advanced Open Water course, we have a skill designed to prove the importance of the snorkel. In full gear, the divers swim laps around the pool with everything but a snorkel. In a class filled with 20 year olds in good physical condition, most hit exhaustion between 5 and 8 laps or 250 to 400 yards! After a break, we give them back their snorkel. Once their heads is comfortably in the water, previously exhausted students easily swim the same distance and more with very little energy use. This skill is designed to produce exhaustion, DO NOT try it without an instructor to keep you safe.

Failure is not an option
Have you really considered what happens if you experience an equipment failure at the surface? An aborted dive can easily result in surfacing away from the dive boat. BC failure, broken fin straps, an un-recoverable free flowing regulator all become more serious problems if you left your snorkel in your bag. Even in an out of air situation, most people take their regulators back once they get you to the surface.

Gearing up?
Every year, several diving deaths occur at the water surface. The majority of these deaths are due to exhaustion. Snorkels may be a drag, but carrying your head out of the water is even worse. Swimming at the surface in full gear without a snorkel will quickly exhaust even the most physically fit diver. The snorkel is sort of a secret seat belt for divers at the surface.

Me? I carry my snorkel on every dive.
I'll even take the pink one.

Source: www.divester.com