Breath-hold training will boost your freediving bottom time and improve your chances of surviving a water-related emergency. Heed these guidelines to safely practice in a pool.

1. Start Small
Practice in the pool's shallow end. Wear a wetsuit even if the water feels comfortable (it saves energy), and use a dive mask that covers your nose so you don't accidentally inhale water.

2. Bring a Buddy
Your friend must monitor you the entire time you're underwater—in case you black out.* Have him tap your shoulder every 30 seconds up to two minutes, then every 15 seconds up to three minutes (the max you should attempt). If you don't respond with an OK signal, he should bring you up.

3. Prep Your Lungs
Before you dive, start with two to three minutes of slow, deep-belly breathing. Relax your abs and push your stomach out. Exhale long, slowly, and deeply.

4. Warm Up
Hold your breath and lie facedown in a dead man's float (unfortunate name, huh?). Be completely still. Come up when you feel that first sensation of needing a breath. Lean against the pool's edge and rest while belly breathing for more than two minutes. Repeat twice.

5. Take a Deep Breath
Now it's time for your breath-hold attempt. Inhale deeply, but don't take such a big breath that it makes you uncomfortable. Float facedown and start holding.

6. Relax Your Mind
You're ignoring a survival instinct. Everything in your body is telling you to breathe. Don't watch the clock. Instead, visualize something relaxing, hum a song, or count pool tiles.

7. Breathe!
When you can't handle it anymore, come up for air. Do not talk. Do not high-five your buddy. Your oxygen levels are already low, so you run the risk of passing out for up to 30 seconds afterwards. Catch your breath, then celebrate.
—AS TOLD TO MARK ANDERS

*Emergency Measures If your buddy blacks out, you need to take immediate action. (1) Expose his face to air and literally tell him to breathe. (2) If he doesn't resume breathing after 30 seconds, give him a couple breaths of mouth-to-mouth resuscitation. (3) After 60 seconds, call 911 and start CPR.