The kayaker is now facing the sinking reality he may never see his kayak again.
"According to the wind, it might be somewhere in the North Island, but according to the currents, it should be somewhere in the far South Island," said Donaldson.
"So essentially the search area is far too big for us to go and have a look."
Mr Donaldson said he accepts that it's "pretty much the end of the search", but is making an appeal to the public for anyone who may still spot it.
"We're down to the point where if a fisherman or someone comes across it out there, then we'd like to know."
The kayak, which was built over the course of five years, was described by Donaldson as his most valuable asset and was part of an $80,000 project to cross the Tasman.
He said while he wants to find the kayak because of its sentimental value to him, he also wants to show the world where he had lived and slept for nearly twelve weeks.
"There's people that want to hear the story, and it's very very hard for them to get a perspective on where I had been living all that long," said Donaldson.
"To be able to show to people just makes is so much easier and so much more relevant."
He is currently preparing a series of presentations to talk about his experience, after receiving an outpour of support and interest in his story.
He is also using the opportunity to send a message to the public about maritime safety.
"I think it was a pretty good example of how people should be looking at safety. It doesn't matter where you are on the trip and how you feel, safety is safety and protocol is protocol."
Even after five years of planning and preparation, Mr Donaldson said he had no regrets about the decision to abandon the transtasman row due to worsening conditions.
"It's one of those things when you're dealing with the sea, you've got to accept it's bigger than you are."
