Dayne, who turns 15 on December 29, went into remission in January after battling acute lymphoid leukemia.
He asked the Make A Wish team about six months ago for a boat for his favourite activity, which is fishing.
"I was expecting a small dinghy, nothing as flash as this.
"I got told it would come near my birthday on the 29th."
Dayne was particularly impressed with the boat's 30 horsepower motor.
"I go fishing as much as I can. I like the adrenalin of catching the fish. I love fishing so much so I was hoping they would let me get a boat."
After backing the boat into the water, Watson cracked open a bottle of bubbly so Dayne could christen his new boat, which he named Apex Fisher. The duo then got on board and began examining Dayne's new gear, which included life jackets, a chilly bin and a VHF radio.
Wish co-ordinator Tim Bird said the Make A Wish team granted wishes to young people aged between 3 and 17 with life-threatening conditions.
"They can wish for absolutely anything and we will make it happen. We always try to add layers of magic that they aren't expecting.
"A wish is something to look forward to through treatment, then something to look back on and draw strength from because, sometimes, it can be quite a rough journey with trips to Starship all the time."
Watson said he had been supporting Make A Wish for close on eight years.
"There's so many kids who love fishing. Whenever there's an opportunity to help some kids who have been doing it tough, it's easy. You just want to do it."
Watson said it had been "really quite special" to be involved with Dayne's wish.
"He lives and breathes fishing.
"This is a gift that will just keep on giving."
Make A Wish
*Make A Wish grants the wishes of children with life threatening medical conditions.
*NZ children aged between 3-17 years old are eligible.
*Wishes will usually fall into one of four categories: To Be - such as a fireman or a zoo keeper; To Meet - a famous celebrity or special family member; To Have - something like a laptop or a playhouse; or To Go, - to a concert, a theme park or the snow.