RIJEKA, Croatia — For almost 30 minutes, Vitomir Maricic didn't take a breath. Face down in a pool, surrounded by anxious onlookers, the Croatian freediver fought spasming pain to redefine what doctors thought was possible.

When he finally surfaced, he had smashed the previous Guinness World Record for the longest underwater breath-hold by nearly five minutes.

But, even with the help of pure oxygen before the attempt, it had pushed him to the limit.

"Everything was difficult, just overwhelming," Maricic, 40, told reporters, reflecting on the record-breaking day on June 14, 2025.

"When I dive, I completely disconnect from everything, as if I'm not even there.

"This time, I struggled mentally and, halfway through, I thought about quitting."

Before the record dive, Maricic inhaled pure oxygen deeply for 10 minutes to prepare his body to go for so long without fresh air, saturating his blood with oxygen.

His doctor watched on with trepidation and uncertainty as Maricic struggled towards the record in a small pool inside a hotel in Croatia's northern coastal town of Opatija.

"It's something completely unknown to modern medicine," pulmonologist Igor Barkovic said.

But Maricic's record of 29 minutes and three seconds without oxygen could open up new possibilities, added the expert in hyperbaric and maritime medicine.

"It opens up new perspectives and perhaps even possibilities we could one day apply to help patients."