The cold water and relatively chilly air temperatures of New Zealand’s Cook Strait proved to be too much for local marathon swimmer and City Councilwoman Kathleen Wilson, who failed to finish a long-distance swim for the first time in 15 years.

Swim resume of Kathleen Wilson

1997: Swim around Key West, Fla., 12.5 miles.

1999: Manhattan Island Marathon Swim, New York, 28.5 miles.

2001: English Channel, England/France, 21 miles.

2003: Tampa Bay Marathon Swim, Florida, 24 miles.

2004: Catalina Island to Long Beach, Calif., 22 miles.

2005: Lake Zurich Marathon Swim, Switzerland, 17 miles.

2006: St. Vincent’s Swim Across the Sound, New York, 15 miles.

2007: Santa Barbara (Calif.) Channel Swim, 20 miles.

2008: Strait of Gibraltar, Spain to Morocco, 11.2 miles.

2010: Charleston peninsula, I-526 bridge to bridge, 16.25 miles

2011: Lake Memphremagog, Vermont, 10 miles

2012: Molokai Channel, Hawaii, 26 miles

2013: Cook Strait (did not finish), New Zealand, 17 miles.

Wilson, 49, of James Island, was stopped with a bit more than three miles to go in the 17-mile swim between the north and south islands when she didn’t respond to directions and was incoherent.

Once aboard the boat, Wilson shook uncontrollably and suffered an array of symptoms of mild hypothermia for the next six to eight hours. Her temperature was not taken.

“I don’t remember leaving the water and was speaking gibberish,” Wilson said in a phone interview Thursday. “I was in bad shape.”

For Wilson, Cook Strait was the coldest of her 13 swims. The water temperature ranged from 62 to 64 degrees, while the air temperature during the day was 68-70. Her next-coldest swim, the 21-mile English Channel swim in 2001, featured water temperatures of 63 to 65, but air temperatures in the upper 70s.

Wilson said Thursday’s cooler air and being 12 years older combined to make it more challenging.

She did not think the swim came too soon after what she previously called her toughest challenge to date, the 26-mile Molokai Channel Swim in September. Molokai took 20 hours and 49 minutes.

Wilson, accompanied on the New Zealand trip by her husband Fred Wilson and friend Leslie Fanning, spent most of the week in Wellington, where they waited for rough seas and wind to ease to give her a chance to complete the swim, one of the prestigious “Oceans 7” swims.

She kept in touch with supporters in Charleston via Facebook and text messages, and expressed worries about her window of opportunity closing on a trip that cost an estimated $12,000.

On the second-to-last day she planned to be there, Thursday in New Zealand, conditions eased enough for her to start at 11 a.m., which is not as ideal as starting at daybreak. After darkness, Fanning attached light sticks on Wilson’s back to keep track of her location before her swim guide, Phillip Rush, decided to pull the plug on the effort.

What’s next?

“It’s too soon to say,” Wilson said. “I’m very disappointed to mar my record with a DNF (did not finish), but when I got into the water, I decided I’d swim until I’m unconscious, and that’s exactly what I did.”