"Any death or even an accident on our waterways is a major concern to the Bay of Plenty Harbourmaster team.
"We put in a lot of effort and resources to try to educate the public around being safe on the water."
Rapson's advice to boaties was to make sure they knew the rules before heading out on the water and stayed safe.
The four deaths were in addition to two other water-related deaths and a death believed to be a result of a shark attack in the North Island already this year.
On January 1, Reece Nahana John Thomas, 36, died after a water incident in the sea at Kaikōura. On January 6, a man drowned in Lake Puketī, southwest of Auckland.
Just after 5pm on Thursday Emergency services were called to Waihī Beach where a woman had been killed by a shark.
Water Safety New Zealand appealed to all people to make wise decisions around water.
"We know Kiwis will continue to enjoy our beautiful waterways as the warm weather continues. We need everyone to take responsibility and think about water safety," spokeswoman Sheridan Bruce said.
"While our waterways are our playground they can be incredibly unforgiving."
Key safety messages included always taking a buddy, swimming between the flags at patrolled beaches, supervising children around water at all times, watching out for rips and always wearing a lifejacket on boats and while fishing from rocks or net fishing.
Surf Life Saving northern region head of operations Alan Gibson reiterated calls for people to take basic precautions to ensure day outings did not end in tragedy.
"We are asking if people go rock fishing that they wear a lifejacket and tell someone where they are going," Gibson said.
"If they are bathing, just to never swim alone and if you get caught in a rip to ride it out and put their hand in the air and seek lifeguard assistance."
Bystanders who witness people in strife in the water should dial 111 or get the attention of lifeguards if they were on a patrolled shoreline, Gibson said.
"Sadly, in New Zealand, a lot of bystander rescues end up in a double or single tragedy for the person who is entering the water to save someone else."
Last year 69 people drowned in New Zealand. The majority of deaths happened in the upper half of the North Island.
- Additional reporting New Zealand Herald