When you're clearing your mask for the first time underwater, it's a good idea to be in the shallow end. Then, when you freak out because you breathed in about a half gallon of water through your nose, you can just stand up.
This is a tip for those who might run where giant swarms of gnats sometimes loiter by the side of the road. This tip stems from a run on the Mayan Riviera in Mexico, but I've encountered swarms of gnats in Virginia and Kentucky as well. After your run, always stop and look in a mirror before going into public. Otherwise, you might actually complete a transaction at the resort store and greet five people before realizing you have up to 15 gnats stuck to your face and neck.