What can you do to keep your snorkel mask from leaking?

You can make your mask tighter but not too much because that can cause more leaking. To check if your mask is properly fitted, you should put the mask to your face, without putting the strap over your head, and breathe in through your nose. If the mask sticks, it is a good fit, if it falls off, you may need to get a different mask. You should also check if your hair is getting in the seal, if so make sure to take the hair from the seal.