Watch a TV program with a mask on (so you are not inhaling / exhaling through your nose) and a snorkel in your mouth.
Any issues?
If yes, explore those.
If no, good, remember that next time you try scuba... it might just be that only breathing through your mouth is throwing you off.
That's true. I never breathe through my mouth. I guess I'll try just breathing normally through my mouth for like a movie or something. Thanks for the idea!