OK, there’s water in your snorkel. Now what?
First, if you are a new snorkeler and didn’t leave the surface, it’s most likely a wave broke over the top of the snorkel, and poured down the tube, or you ducked your head down a little too low, and you probably aren’t expecting it. The first way to avoid that is to EXPECT it to happen, and know what to do.
Even if you have exhaled normally, most snorkels have a pretty small volume, and most of them also have a purge valve in the bottom end, so it really doesn’t take much to blow them clear. At the first hint that water has come down the tube, give a short hard last of air into the mouthpiece. This will almost certainly clear it so you can inhale safely again right away. It’s really a good idea – especially if you have never had any professional instruction – to just stand in chest high water, lean over, take a breath, and duck your head down so the snorkel top is below surface level, and let it fill. (You’ll hear it gurgling in). Lift your head a bit, and then blast it clear. Do this again and again until you are comfortable, and then lie on the surface and repeat. It’s actually very easy.
If you are coming up from a breath hold dive, you probably really want that first breath. In this case, tip your head back a bit – it’s always a good idea not surface fast without seeing what’s overhead – and when just a few feet below the surface, start exhaling a small amount of air into the snorkel. This will displace most of the water in the snorkel. As you break the surface, a short final blast will completely clear the snorkel, and it will be ready for that first inhalation. This works well with snorkels equipped with a purge or without.