"Our whānau wish to express our huge appreciation to all the services and the many volunteers and whanau searching for him."
Flavell is Māori, approximately 6 foot 1 inches with shoulder-length wavy hair and has a light moustache and goatee.
He was wearing black cargo pants, a printed black long-sleeved T-shirt with the number 53 on the sleeve, and a dark blue beanie.
Anyone who may have seen Flavell or has details about him was asked to contact police on 105 and quote job number P051519937.
Earlier, police also appealed for information from occupants of any vessels that left Mokoia Island between 2pm and 5pm on Wednesday, August 10. Boaties were encouraged to contact Rotorua Police, either in person or via 105, if they did.