Bethany Hamilton says she'll never compete as a disabled surfer, despite having her left arm completely severed by a tiger shark at the age of 13.

Key points: Bethany Hamilton was attacked by a 4-metre tiger shark in Hawaii in 2003

Bethany Hamilton was attacked by a 4-metre tiger shark in Hawaii in 2003 She returned to the surf one month after the attack and has a slightly modified board

She returned to the surf one month after the attack and has a slightly modified board She has announced she'll be competing on this year's WSL qualifying series tour

The 30-year-old Hawaiian surfer doesn't want to be defined by her missing limb and says it has made her a stronger competitor.

"If I thought of myself as disabled I wouldn't be where I am today," she said.

"My surfing is at the level of the best of the best so it's only natural I compete against the best of the best."

One month after the attack in October 2003 Hamilton returned to the surf and within two years she had won her first national title against able-bodied surfers.

"Once I got my first wave there was no turning back.

"I was on a mission to become the best surfer I could be, regardless of what my body looked like," she said.

Hamilton is determined to use that same grit to make her surfing comeback after taking a break from professional competition since 2018 when she gave birth to her second child.

Hamilton says adjusting to surfing with one arm has required extra strength training. ( WSL )

She announced in Sydney today she will be back competing on this year's World Surf League (WSL) qualifying series tour, with the goal of qualifying for the 2021 WSL World Championship Tour.

"This year all of my focus is on competing, I want to thrive on the world tour.

"I have a lot of work to do all the girls on the tour are surfing insane so there's no room for error."

'Of course it's incredibly hard'

Adjusting to surfing with one arm has not been easy.

Hamilton has to kick and paddle harder than her competitors and uses a handle on the tip of her board to help her dive under waves — otherwise she uses a standard-competition surfboard.

"The main thing is keeping my body strong so that I can compensate well," she said.

"Of course it's incredibly hard, it was just a matter of adapting to how to do it with one arm."

Hamilton prefers not to dwell on the past and focuses on what she can achieve. ( Supplied )

If Hamilton qualifies for the 2021 WSL at 31 years old, she will be one of the oldest on tour and the only woman with children to compete.

"I love bringing them along, they make it so exciting and it gives me balance mentally, rather than thinking of being my best and surf, surf, surf, it's like, no I have to go home and be Mum now."

She experienced one of her best years of competition in 2016, beating six-time world champion Stephanie Gilmore and then top-ranked surfer Tyler Wright when she took third place in the Fiji Women's Pro Competition.

On top of that she charged 12-metre waves, earning a WSL Big Wave award nomination surfing the Jaws in Maui, six months after giving birth to her first child.

Her key to success is focusing on what she can achieve.

"If I moped around thinking how I only have one arm then I would have had a very different life.

"I approach life in what can I do and I just want to be my best."