Triathlon Swim With a Snorkel?

A few days ago I was reading a triathlon forum when I came across a thread that said triathlon swimming with a snorkel is it fair? I was intrigued by the forum post and clicked into it to see what it was about. It turns out that people are doing their swim segment of their triathlon wearing a snorkel!? They guy who posted the link also said that it turns out it is not against the rules.....

I think that this gives one an advantage and should be against the rules. It would seem that if you don't have to keep coming out to breath and are good at swimming with a snorkel then you could in theory be faster. Maybe no the fastest but faster. Apparently people also use this snorkel technique in the pool where you do not even have to poke your head out to see where you are going.

Maybe I'm wrong and just jumping to conclusions, any thoughts? Should it be triathlon race legal to swim with a snorkel?