Scott Donaldson's hopes of retrieving the kayak he spent three months crossing the Tasman in appear to have sunk along with the vessel.
Yesterday his kayak was spotted 20 nautical miles northwest of Farewell Spit, near Nelson.
Donaldson had abandoned the craft last week after he suffered head and chest injuries in what he said was the "nastiest night" he had experienced during his attempt to cross the Tasman. Conditions became dangerous and he had to be rescued by helicopter.
He was on the brink of reaching his goal of becoming the first person to paddle from Australia to New Zealand, and was just 83km off the coast of Taranaki when he was airlifted off the kayak.
Taupo rescue pilot John Funnell, who dropped Donaldson food and water when he ran low on supplies, spotted the kayak yesterday.
Donaldson went out last night on a chartered boat, while Funnell guided them by air, to retrieve the kayak.
By the time they reached the signal from the vessel's tracking beacon, it had broken off from the kayak and the craft was nowhere to be seen.
Forced to give up when it got dark, Funnell and Donaldson flew out again this morning for an hour and a half, but again found nothing.
"Unfortunately the sea conditions were starting to cut up a bit when we left - nothing horrendous, but a few white caps appearing which makes it difficult when you're looking for a little 6m white boat," Funnell said.
It was likely the kayak had sunk, he said - it was on its side and taking on water when they last saw it yesterday.
Funnell would not be flying out to look for it again until they had a confirmed sighting, he said.
"It's too big of an ocean and too small of a target we're looking for without some form of tracking on it.
"Scott's probably pretty disappointed, it's quite an expensive boat."
Formerly of Rotorua, Donaldson, 44, left Coff's Harbour in New South Wales headed for Port Taranaki on April 19.
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