O2 — Breath Hold Apnea Trainer

Train your breath like a professional freediver.

O2 is a science-based breath-hold training app that helps you extend your breath-hold time, build CO₂ tolerance, and improve mental focus through progressive training protocols.

PROVEN TRAINING METHODS
• CO₂ Tables — Build carbon dioxide tolerance with decreasing rest intervals
• O₂ Tables — Extend breath-hold capacity with increasing hold times
• Box Breathing — The 4-4-4-4 technique for stress relief and focus
• Progressive difficulty levels from beginner to advanced

BUILT FOR PERFORMANCE
• Designed for freedivers, spearfishers, swimmers, surfers, and athletes
• Used by professionals to prepare for competition and improve underwater performance
• Backed by established breath-hold training science

SMART TRAINING EXPERIENCE
• Haptic feedback guides you through each phase without looking at the screen
• Voice cues announce hold and breathe phases
• Visual timer with clear phase indicators
• Track your progress with detailed statistics

HEALTH INTEGRATION
• Sync workouts to Health Connect
• Track your training consistency
• Monitor progress over time

SIMPLE & FOCUSED
• Clean, distraction-free interface
• No subscriptions — one-time purchase unlocks everything forever
• Works offline, anywhere

Whether you're training for freediving competitions, improving your surf hold-downs, or simply want to experience the mental clarity that comes with breath control — O2 gives you the tools to progress safely and effectively.

Start your breath-hold journey today.