Hi Cinebelle and welcome to the board.
I recall that my instructor TOLD me to always exhale through my nose, it minimizes the possibility of getting water up your nose if your mask gets knocked off for some reason. Also, if your snorkel is hooked to your mask, that can be a problem too, every time the snorkel moves, it will move the mask a little.....I fold up my snorkel and put it in the pocket of my bcd.
I recall that my instructor TOLD me to always exhale through my nose, it minimizes the possibility of getting water up your nose if your mask gets knocked off for some reason. Also, if your snorkel is hooked to your mask, that can be a problem too, every time the snorkel moves, it will move the mask a little.....I fold up my snorkel and put it in the pocket of my bcd.