New Zealand’s freediving champion William Trubridge is expected to complete his dolphin-like 22km swim across the Cook Strait largely in under 10 hours this evening.

He was due to finish up between 6pm and 7pm this evening, after embarking on his swim from Wellington this morning in a personal effort to highlight the plight of endangered hectors dolphins.

Surfacing for just seconds every 25 metres or so to catch his breath in the same way a dolphin would, the swimmer is being supported by a team in a boat and two kayaks, which are guiding him in the direction of shore.

His father David Trubridge told Checkpoint a bland, carb-rich diet of potato soup, cooked by his wife Linda, was sustaining Mr Trubridge in his efforts, which included battling a strong northerly tide, pushing him southwards this morning.

“He’s swimming across under water,” Mr Trubridge said.

“He dives down, swims under water for about 25m and comes under for 10 seconds, taking a few deep breathes and he dives back down and carries on, and he does this all day continuously across Cook Strait.

See Radio New Zealand