She said there were 45 dedicated dunkers and more than $4000 had already been raised, with more funds still to come in.
Image 1 of 7: Life Education Trust Dunk for Harold at Tikitapu (Blue Lake).
They had been running Dunk for Harold for more than 10 years, she said.
The event also included rocks children could decorate - some of which had spot prizes under them - a sausage sizzle and raffles.
A $2000 travel voucher was up for grabs and for every $100 a participant raised they got an entry in the draw.
Ms Brackfield said the event was about having fun in the community and raising their profile.
She said Life Education Trust Rotorua saw 6000 children a year, which was a big commitment and they had to find the funds to keep running it.
Dunker Julie Voss, who took part in a submarine costume, said she had been nervous beforehand because she could hardly see.
She said it was a lot colder than she was expecting in the water.
"It was great fun."
She said Life Education Trust Rotorua was a great cause to get behind because it supported children and went to all schools, teaching them about who they were, being healthy and being confident.
