If you’re out on the water, maybe fishing or just going for a swim, you may find yourself needing or wanting to spend some time beneath the surface. Maybe you’re looking for something you dropped, hunting for Catfish to noodle, or avoiding detection from people on shore… regardless of why you’re under water, there’s one thing you can do to improve your chances of surviving it.

Most of us tend to take a number of deep breaths before holding our breath to submerge — that’s a bad idea. Hyperventilating before you go under doesn’t actually increase the amount of oxygen in your blood stream — what it does do is decrease the amount of CO2. That might sound good, but it’s not.

That CO2 in your blood stream is what alerts your brain that you need an influx of fresh oxygen. With a reduced level of it, you can’t actually hold your breath for longer, you just feel like you can. That dramatically increases your chances of holding your breath until you pass out — something commonly referred to as a shallow-water blackout.