Luckily, fire fighters were able to throw him a life preserver.
The Hamilton Police rescue boat was deployed, which brought the dingy and the children to shore.
Both children were wearing life jackets, but their father was not, Mr Bu Bear said.
"On reflection it would have been better for him to have called 111 and reported his boat being in difficulty and remained in the vessel instead of putting himself at risk.
"With the weather improving and the onset of daylight saving this incident could be a good catalyst to encourage boat owners to ensure their vessels are in good condition before heading out on the water."
Coastguard education spokeswoman Heather Murray said it was great the man had a phone with him, but two forms of communication were recommended - including a VHF radio which can be heard by more than one person when used.
"If you get into difficulty call for help on VHF radio or mobile phone and wait in the boat, only enter the water as a last resort," Ms Murray said.
"It's fantastic the children were wearing life jackets, but he had one too - but wasn't wearing it."
Parents should set a good example for their children by wearing a life jackets and taking a secondary form of propulsion such as paddles for when unforeseeable engine problems arise, she said.