Mr Weatherall said concern about water safety "ramped up" in recent weeks because of international media reports about radiation levels at Fukushima being higher than thought previously.
"So we sought advice from the Japanese authorities, New Zealand authorities, and Australian authorities about the level of risk that we potentially will be exposed to," Mr Weatherall said.
"We've had a couple of people who have had concerns . . . but there's no issue as far as I'm concerned."
Mr Weatherall said they were given sound advice and letters from the International Lifesaving Federation confirming the safe status of the water at Onjuku Beach but he still had the ability to pull the team out of the competition after they landed next week, if need be.
Papamoa coach Kurt Wilson said he was initially worried the Japanese might not have been open enough about the status of their water quality.
"I was a bit scared they might be biased in the information they [gave] us, but their information matched exactly with the independent information we got," he said.
"They've given us reports saying it's all good and looks good to go."
Mr Wilson, who is one of seven officials travelling with the athletes, said the trip to Japan had been planned for years and it was common knowledge the Fukushima power plant was "hammered" in the 2011 earthquake and tsunami.
Omanu coach Donal Boyle said he was worried about the water safety at Onjuku Beach but comforted to learn the main currents flowing past the eastern side of Japan flowed north.
"That's pretty much most of the direction where the radiation is going to go, not south which is where the champs is."
Onjuku Beach is located about 250km south of Fukushima.
"We are concerned, but the athletes just want to go there and compete."
Under 19 New Zealand Iron Woman champion Natalie Peat said she had faith in the water testing results.
"Obviously athlete safety was the number one priority. We were fairly concerned," she said.
"If they had come back and said there were moderate to high levels, we would have obviously considered pulling out."
Ms Peat, who will compete as a senior from Papamoa club, said Surf Lifesaving New Zealand had kept competitors updated with any developments "but the general consensus was that it was going to be safe and any issue, we would have been told straight away".
"We are all just really excited to go out and race. Safety was the number one thing we are just really looking forward to getting there and competing."
Bay of Plenty club development officer Scott Bicknell said the matter was a speed bump in the preparation of the competition but athletes were keen and ready to go and there was no concern anymore.
New Zealand took the championship title from Australia when the event was last held in 2011, at Mount Maunganui.
