Make sure that the skirt of the snorkeling mask (the plastic seal that fits your face) is flat with no hair stuck under the seal. If you are sporting a mustache you can either cut it off (yikes!) or put some Vaseline on your mustache to help provide a seal. Do not tighten your snorkeling mask too much as this flattens out the round shape of the skirt preventing a proper fit, and, keep the snorkeling mask strap in the middle of the back of your head with the strap above the ears. If you do get a small amount of water in your mask (lines on your face when you smile at the fish) blow out through your nose while applying pressure on the top of the mask frame.