He also cleaned up in the school 50m and 100m freestyle events. Speed in the pool is a key part of his dominance in water polo.
His club coach from Marist helped facilitate the move to New Zealand, as Kolasinac was looking to broaden his horizons, better his English and play some competitive water polo.
"My first plan was America, but when I saw King's College on the internet, I said 'Why not?' It's amazing here," says Kolasinac, whose English is very good when you consider he has been in New Zealand for only three months.
He's not just cruising through his schoolwork, either, taking maths, chemistry, physics and biology along with English.
There is no problem with communication in the pool. If he wants the ball, he makes it known, and more often than not his teammates feed him.
He can be devastating at times, such as when King's beat Sacred Heart in February for the first time in many moons.
They repeated the dose at last month's nationals in Wellington, although Sacred Heart turned the tables to win the Auckland final 9-6.
Some of the experience and tactical and technical knowledge that Kolasinac is passing on to his teammates is priceless. In turn, he feels there are some talented players at King's and that the team has been unlucky at times this season. King's coach Jim Floerchinger also coaches Kolasinac at the Seawolves club.
Kolasinac says the number of training sessions is the main difference between water polo in Serbia and New Zealand. In Serbia, he habitually has 12-13 sessions a week with less than half that in New Zealand.
"It's tough to organise here because school takes a huge part of the day. But I am really grateful to be here."
The next big competition on Kolasinac's agenda is the July Pan Pacific championships in Auckland, when he will turn out for the Seawolves at under-18 and under-20 level. Kolasinac is unsure what he will do beyond this year but might stick around for university.
Serbia, it seems, can wait as Kolasinac banks life skills and broadens his horizons.
