On June 14 in Opatija, Croatia, Vitomir Maričić slipped into a hotel pool, inhaled one last breath of pure oxygen, and disappeared beneath the surface. He stayed there — motionless, silent — for 29 minutes and 3 seconds. When he finally surfaced, the Croatian freediver had not only broken a Guinness World Record. He had redefined the edge of what the human body can endure.
The feat stunned both scientists and spectators. The average person can barely hold their breath for a minute. Even elite divers, without special preparation, struggle to cross the ten-minute mark. Yet Maričić more than doubled the diving stamina of a bottlenose dolphin and matched the performance of a harbor seal.
Bending Biology With Oxygen
Humans aren’t built for long breath-holds. Our lungs replace only about 20 percent of their volume with each breath. Seals and dolphins do far better — up to 90 percent — making them natural champions of the deep. To even the odds, Maričić used a trick from medical science: breathing pure oxygen for ten minutes before his attempt.
This process, called denitrogenation, flushed nitrogen from his blood and packed his body with oxygen. “I started my record-breaking attempt with nearly five times more oxygen in my body than usual,” he explained in an Instagram post. That oxygen filled his red blood cells and dissolved directly into his plasma, a reservoir that normally carries very little.
Doctors sometimes use this technique to buy unconscious patients extra time without breathing. But Maričić pushed it far beyond the hospital setting. Guinness officials and 100 onlookers watched as he lay face-down in a three-meter pool, unmoving, while five judges timed the attempt.
Still, no amount of oxygen makes half an hour underwater easy. “It’s not about how much you inhale, it’s about how little you need. No panic, no thoughts, just silence. That’s how you make it to 29,” Maričić said.
Don’t Try This At Home
Breathing pure oxygen isn’t without danger. Too much can cause oxygen toxicity, leading to dizziness, convulsions, or blackouts. There’s also the risk of carbon dioxide toxicity, when CO₂ builds up in the blood unnoticed. “Do have in mind, diving with pure O2 can be dangerous and even fatal,” Maričić warned his followers.
He’s not exaggerating. The previous oxygen-assisted record, set by fellow Croatian Budimir Šobat, stood at 24 minutes and 37 seconds. Before that, magician David Blaine held it for 17 minutes on live television. Few people attempt such stunts, and fewer still emerge unscathed.
The world record for the longest someone has held their breath without oxygen assistance is 11 minutes and 54 seconds, set by Branko Petrovic in 2014. Heike Schwerdtner holds the record among females, after she held her breath without oxygen assistance for 9 minutes and 22 seconds.
Even without oxygen, Maričić can hold his breath for more than ten minutes — an ability he’s honed through years of training. He also used to hold the record for the longest underwater walk on a single breath, covering 107 meters. That’s until just recently, in August, when Polish diver Stanisław Odbieżałek set a new record at 110.7 meters.
But for Maričić, the point isn’t just bragging rights. According to Guinness, he dedicated his June attempt to raise awareness about ocean conservation. It’s a reminder that the seas he trains in are under threat — and that even human extremes pale next to the challenges marine ecosystems face.
