An Australian swimming coach whose wild victory celebrations at the Tokyo Olympics went viral online has apologised for tearing off his mask in defiance of strict coronavirus rules.

Coach Dean Boxall flipped out after his swimmer Ariarne Titmus clinched gold in the 400m freestyle ahead of fierce American rival Katie Ledecky on Monday.

Roaring with delight, the shaggy-haired swim guru kicked the air and hammered his fists, before thrusting his hips against a perspex barrier.

He also tore off his face covering and threw it across the Tokyo Aquatic Centre's spectator-free stands as an anxious volunteer hovered nearby.

Boxall has embraced the moment of online fame that has seen him dubbed "Ultimate Warrior" in honour of an over-the-top US wrestler from the 1990s renowned for pounding the ring ropes.

However he admitted he went too far breaching the Covid-19 protocols imposed in an attempt to keep the Games bio-secure as host city Tokyo endure a virus-induced state of emergency.

"I need to apologise, actually, because I tore my mask off and it ripped," he told Australia's Seven Network. "I just lost it in the moment."

Boxall said he lost control after working with Titmus for six years and seeing her "execute to perfection" a plan to overcome US great Ledecky.

"It just came out," he said. "It built up in the trials, it was coming through and then when I saw the race unfolding I couldn't keep it in."

Boxall told Australian media: "I think I went outside of my body."

Titmus said after the win that she had only seen snippets of Boxall's celebrations but they fitted her coach's larger-than-life character.

"That's just the way Dean is," she said. "He's very passionate about what he does and he becomes quite animated.

"He puts 100% into being a swimming coach and he's sacrificed a lot of his family life with his kids and his wife for his job."