"You can never have too many girls," he says with a laugh, as more than 1500 teenagers will orchestrate paddling power as 12-person and six-person teams as well as individuals in myriad classes in under-16 and under-19 divisions.
It is touted as the biggest high school tournament - second only to Maadi Cup rowing in the country which started this week - where paddlers will compete over 250m and 500m distances.
The six-person 500m teams will face the daunting task of negotiating a hairpin turn at the halfway mark.
Hastings Boys' High School, Napier Girls' High School, Sacred Heart College, St Joseph's Maori Girls' College, Te Aute College and William Colenso College are among the equation when the four-day tourney gathers momentum this week.
NBHS were the only Bay school to make it to the main championship division last year, bowing out in the semifinals to be the sixth (250m) and seventh (500m) ranked boys' six-member teams in New Zealand.
This week Tamaiva-Eria expects Gisborne Boys' High and last year's plate finalists, HBHS, to mount solid campaigns.
"I can't say who'll win. It will come down to who does best on the day."
Huntly College (U19 boys) and Nga Taiatea Wharekura (U19 girls) stamped a level of ascendancy last year in the 25-year-old championship.
All the other Bay schools have battled it out in plate and bowl sections.
Tamaiva-Eria, a third XV NBHS rugby player, took up the sport because he wanted to learn something different.
"It's on water, so you don't use your legs that much. You use your upper body," says the prop, who finds parallels between waka ama and rugby.
The sense of cohesiveness and timing in paddling is similar to the mechanics of a rugby scrum when a hooker feeds the ball before the front row drive, relying on their backrowers to put in a concerted effort.
Rere Chase, 17, of NGHS, Jessie Quinn, 15, of William Colenso, Eikura Albert, 17, of St Joseph's Maori, and Summer Crawford, 15, of Karamu High, all attest to how imperative it is to find a sense of timing.
Strength and endurance are vital but minus technique they become ineffective.
William Colenso manager Anne Butcher says the youngsters are able to foster a sense of camaraderie when sitting on the shore at Pandora Pond or Clive River waiting for their turn to paddle at training.
"It's not a solo sport so the six of them all have to be good friends," says Butcher, adding their kaumatua (elder), Tamihana Nuku, who has been to the world champs and paddled in the over-60s grade, often inspires the teens.
Says Chase, who has been paddling since she was 7: "It makes me feel calm and relaxed."
Quinn has represented her school twice and the Maraenui Sports Club once.
All the pupils paid tribute to their coaches for instilling a hard-work ethic.
In Quinn's case, coach Ian Matehe ensures they are motivated.
Albert, who has been paddling for the past five years, highlights the significance of culture in the code.
"It helps me stay strong to my roots," she says, mindful how several waka came to this country bringing in the different tribes from Hawaiiki.
Crawford, a year 11 pupil, says while Karamu High won't compete this week they are already preparing for next year.
The school lost several paddlers who have gone to other schools or overseas.
"I'm injured [knee cartilage] but I paddle in the W6 team," says Crawford who also plays touch, netball and basketball.
Like Tamaiva-Eria, she relishes the benefits between codes.
"Waka ama helps strengthen my arms for netball and basketball. It also helps with my dancing," says the member of the Born to Move Dancing Studio in Hastings.
A Waimarama Surf Lifesaving Club member, Crawford joined the Heretaunga Ararau Waka Ama Club in Clive two years ago when a surf mate recommended it. She says Karamu High principal Martin O'Grady supports waka ama.