Henderson won the women’s title at the national championships, while Piha’s Elliot Paerata-Reid took the men's title.
The day produced clean waves of up to 1m with offshore winds, but the swell size decreased through the afternoon and the incoming tide turned the swell tap off.
Fourteen-year-old Henderson became the second-youngest winner of the open women’s division, adding to her under-18 title earlier in the day.
She posted a 14.03 total to beat Piha’s Gabrielle Paul by nearly three points in a dominant display.
Dunedin’s Hayley Pascoe finished fourth.
"I started to believe I could win when I got a five and I only needed another five to lead, and I had already got that score and I hadn’t actually surfed to my potential," Henderson said.
"I knew if I got a few good turns in, I could get a six or higher, you know.
"Then when I was leading toward the end, all I wanted was for the time to speed up because I had priority and I knew I could control the final."
Henderson also claimed the overall standout performance of the event.
"I am so stoked on the win — I can’t really believe [it], but yeah.
"I mean my goal was to win the 16s at this event and do well in the 18s — I wasn’t actually going to do the opens, but I convinced Mum to let me, and now I have won."
He scored 15.17 to edge Stairmand’s 13.80.
"That is my fourth final in a row," Paerata-Reid said.
"I have won every semifinal for the last three years and beaten the eventual champion each time so I knew I could do it. I just needed to put it together in the final.
"I didn’t really feel like I did my best surfing until the final this week. I had a bit more to give but yeah, I just looked at it a bit more like a job this week and took it heat-by-heat and it worked."
Dunedin’s Elliott Brown featured in the semifinals, although was unable to progress to the final.
Meanwhile, Dunedin surfers claimed two titles in the age-grades.
Alexis Owen scored 11.43 to win the boys under-14 division, while fellow Dunedin surfer Karne Gabbot came in fourth.
In the men’s over 40 grade, Lyndon Fairbairn scored 11.8 to edge Kaikoura’s Alan Te Moananui and claim the title.
Christchurch surfer Ambrose McNeill claimed the longboard division on Saturday with a convincing victory and 12.6-point heat total, surfing in the national championships for the first time in several years.
McNeill defeated two-time champion Zen Wallis (Piha), who finished runner-up ahead of early standout Cameron Haylock (Christchurch) and Billy Whelan (Mangawhai).
In the women’s longboard division, Gabi Paul (Piha) defended her title with a 10.0-point heat total, with Jo Moore (Taranaki) finishing in second, Donna Henderson (Christchurch) in third and Tegen Bishop (Christchurch) in fourth.
Stand-up paddleboard titles went to Jamie Andrews (Taranaki), who defended his title, while 14-year-old Amelie Wink (Christchurch) claimed the women’s division.
Senior titles went to Taranaki’s Jarred Hancox (over 35s), Dunedin’s Simon Brennan (over 45s) and Raglan’s Geoff Hutchison (over 55s).
Women’s titles went to Dunedin’s Hayley Pascoe (over 30s), Dunedin’s Tash Civil (over 35s), Christchurch’s Donna Henderson (over 40s), Dunedin’s Ange Reardon (over 45s) and Hawke’s Bay’s Marguerite Vujcich (over 60s).
