Kennelly turned professional at the age of 17 and soon began surfing in the World Qualifying Series (WQS). After finishing 2nd in the world on the WQS Tour in 1997, she was accepted to the World Championship Tour and quickly began earning victories at some of the tour’s biggest events. Kennelly began a string of successful visits to Teahupoo, Tahiti in 1998 when she won the Gotcha Black Pearl Women’s Pro. She would go on to win 3 more times in Teahupoo in 2000, 2002, and 2003.

2003 was a breakout year for Kennelly as she peaked at number 1 in the WCT rankings before ending the year ranked as the 2nd best female surfer in the world. In addition to her win in Teahupoo at the Billabong Pro, she garnered victories at the Roxy Pro in Fiji and the Turtle Bay Pro in Hawaii as well as a 3rd-place finish at the Maui Billabong Pro. Her various top finishes won Kennelly the year’s coveted Triple Crown of Surfing. Kennelly maintained a spot in the top 10 of the ASP rankings through 2007, with numerous top finishes and groundbreaking female performances. This included a 2nd-place finish at the Billabong Pro Maui, a team gold medal at the 2007 Summer X Games, and a record-setting ride in 2005 as the first-ever woman to tow in at Teahupoo.

After leaving the World Championship Tour in 2007 to pursue acting, Kennelly returned to surfing as a professional freesurfer. She continued to make history for female surfing when she won the first women’s big wave contest at the Nelscott Big Wave Classic in 2010, opening the door for more female big wave surfing competitions in the future. Later that year, Kennelly had a tow-in at Puerto Escondido that is considered to be arguably the best barrel by a female to date.

In 2011, Kennlly chased one of the biggest swells to ever hit Teahupoo. During that infamous ‘Code Red’ swell, she displayed the best barrel-riding by a female at Teahupoo. Three days later while riding in a memorial heat for Andy Irons during the Billabong Pro Men’s WCT, Kennelly suffered a massive facial injury. After getting barreled, she was pushed down to Teahupoo’s notoriously shallow reef and received a severe gash to the side of her face.

She was the female 2018 Big Wave World Champion.

Kennelly’s accomplishments have garnered her numerous accolades, including being named the 2002 Female Surfer of the Year by ESPN and more recently, the 2011 and 2013 Billabong XXL Girls Performance Award, and the 2014 Billabong XXL Womens Performance Award. She was inducted into the Surfing Walk of Fame in Huntington Beach, California as 2013’s Woman of the Year.

In 2016, she won the Pure Scot Barrel of the Year Award at the XXL Big Wave Awards for getting barreled at Teahupoo, Tahiti. This award makes her the first woman to win in any open-gender category. Later that same year(2016) she was nominated for an ESPY Award. At the end of 2016 Kennelly made history once again by becoming the first female ever invited to the prestigious Eddie Aikau Big Wave Event.