How to Dive While Snorkeling
- 1). Lie on the water's surface with your face and stomach facing down. Take three or five full, deep breaths to store extra oxygen in your body. Don't take more than five deep breaths; if you start to feel light-headed, wait to dive or you may faint underwater.
- 2). Take in a final breath. Kick your legs up in the air and push your head down at the same time. Use a breaststroke to descend, if necessary.
- 3). Hold your nose closed. Blow firmly into your blocked nose as if you were sneezing. Listen for a popping sound in your ears, which means you've emptied your sinuses. Continue descending if blowing your nose emptied your sinuses.
- 4). Remain underwater for as long as you feel comfortable. Let buoyancy return you to the surface when you need air. Don't panic.
- 5). Clear water from your snorkel by blowing hard immediately before you reach the surface. Repeat steps 1 through 3 to dive again.
Source...