smrtblnddiver once bubbled...
Don't use one. I find it much more comfortable to just surface swim on my back.
I find that I am most comfortable swimming in the "Sea Otter" position on the surface, as you do, Melanie.
One time, however, our group surfaced to find the boat gone (due to engine trouble and wind drift). The chop was heavy, and the wait was long. Eventually, we ran out of gas and could not breathe the regs any longer. At that point, with the chop slopping over our heads, we all began to wish we had our snorks.
Since then, I have made it a point to carry one in a pocket. They definitely have their uses!