A fitting water birth: Kiwi world champion freediver William Trubridge becomes a father

William Trubridge and partner Sachiko Fukumoto with baby Mila, who was born by water birth at the Trubridge family's Havelock North home. Photo / Facebook

Kiwi freedive world champion William Trubridge is a father.

Trubridge has announced his partner, Sachiko Fukumoto - an actress and also an avid diver, gave birth to a baby girl named Mila at the Trubridge family's Havelock North home on March 16.

In a nod to the pair's shared passion for diving, Mila was born via water birth.

Trubridge said he was in "awe and astonishment" and said being a father had already transformed his life.

William Trubridge in the waters off Tokashiki Island, in the Okinawa islands of Japan, with his partner, Sachiko Fukumoto during their pregnancy. Photo / Kazunori Nagatani

He also said he had new admiration for all womanhood after Fukumoto's 13-hour labour to give birth naturally.

Trubridge said the couple originally wanted Fukumoto to give birth in the sea, but couldn't because the water off Hawke's Bay's coast in March would have been too cold.

The fallback was a birthing pool at the family home in Havelock North.

Trubridge, 38, who was born in Britain but moved to New Zealand when he was 18 months old, holds 18 world records in various dive disciplines.

He set his latest record in 2016 when he plunged 122m into a blue hole in the Bahamas, beating his previous record.

The couple plan to shoot footage with a New Zealand film crew over the next few months for a video project revolving around the childbirth.