Boyle said she enjoyed the Bay of Islands Classic even though she was on her own for most of the race.
"Racing in the ocean is very different from the pool especially when you are swimming alone and it is nice when you get to see the end," said the Commonwealth 800m champion.
"I was going well at the beginning but when Charlotte went past me she kept extending the gap so I just went at my own pace.
"My focus now turns to training as we have a big long-course season ahead of us right up till July, though I will be back for the King of the Bays in April."
Boyle was a popular drawcard to the thousands who lined Paihia Beach during the event, signing autographs and posing for photographs with many adoring fans.
"Open water swimming is so important in New Zealand because we are surrounded by water and being out in nature in the sun is such a great way to enjoy what we have in this country," she said.
Meanwhile, in the men's race, Yasu Hirai made a stunning debut in the Swim Series with a win. Japan's top-ranked open water swimmer beat his Bond University clubmate George O'Brien by 15 seconds.
Hirai, 24, sat in second place for most of the 3.3km race from the historic town of Russell, firstly behind Troy Balvert - of the St Peter's Swimming Academy - who led until the halfway mark, and then on the feet of O'Brien.
"I'm very happy to win in my first Series in New Zealand," said Hirai, who put on an impressive burst of speed with 300 metres to swim.
"I tried to conserve energy as I have some speed at the end and that was what I needed today."
Philip Ryan was the best of the Kiwis, 12 seconds behind O'Brien in third.
Ryan led briefly at the fourth marker when the field closed up but by the fifth buoy the winner was only going to be one of the visitors and as they passed the moored yachts and headed towards the large crowd on the beach it was Hirai who claimed the honours.
Almost 700 competitors competed in round one of the race series which continues in Auckland on December 7.
