I caught a show on the National Geographic Channel last night about a sunken Australian Submarine from WWI.

They sent divers down to check it out.  I was trying to fall asleep at the time, but the voices in the show caught my attention.  Because they sounded like they were on helium.

They were.

It turns out that in certain conditions divers mix helium with their oxygen to avoid the affects of “nitrogen narcosis.”  The positive effect: no “nitrogen narcosis,” which sounds rather uncomfortable.  The downside: communication gets a little tough when everyone sounds like chipmunks.

For a brief history of mixed gas diving, head here.