None of the five people in the boat on that day were wearing lifejackets.
"William's death is a tragic reminder to all people who go boating on our lakes to wear a lifejacket."
Labour weekend is traditionally the start of recreational boating on the lakes.
Bay of Plenty regional harbour master Peter Buell said it had been an excellent start to this year's fishing season, with people having the correct safety equipment on board when checked.
"We're encouraged that the message about lifejackets seems to be getting through, with most people having more than enough lifejackets of the correct size for everyone on board," he said. "Let's keep it going all summer."
In a recent survey 78 per cent of boaties said they always wore a lifejacket on the water, and 60 per cent said they always wore lifejackets and ensured others on their boat did too.
Two-thirds of the people who died last year were likely to have survived if they had worn lifejackets and more than 90 per cent of people who die while recreational boating are men.
The three key messages for all boaties this weekend are: prepare your boat and make sure it is safe; check your gear, make sure it is safe and you have the right equipment; and know the rules and bylaws for boating in the region