Bethany Hamilton was only 13 years old when she lost an arm in a shark attack but that did not stop her from pursuing a career as a professional surfer. Achieving success in her '20s despite her physical limitations, Hamilton started another life journey that triggered new fears and she revealed how she overcame them in the new documentary "Bethany Hamilton: Unstoppable."

The surfer admitted that she initially had a hard time embracing motherhood when she found out she was pregnant with husband Adam Dirks. As with any first-time parent, she had a lot of fears before Tobias arrived in 2015.

But beyond that, she could not imagine how she would handle caring for her child with just one arm. She also was at the height of her career when she became pregnant and while she dreamed of becoming a mom, she did not know how much of this new phase would impact her life as a surfer.

Hamilton, who was the subject of the 2011 film "Soul Surfer," tried to keep the good news from her fans around the world until she realized something else. She said: "As I started to see his excitement and, like, the other people's excitement around me, I was like, wow, this is a gift from God."

Filmmaker Aaron Lieber documented Hamilton during her pregnancy and the surfer learned something new about herself from the experience. She realized that despite her lost arm and her growing baby belly, her surfing actually got smoother and better while pregnant.

The documentary also features family clips from Hamilton's childhood. One footage showed Hamilton, who is a Christian, talking to her best friend Cheri just before the shark attack. Cheri asked if she ever worries about sharks when she surfs and Hamilton replied that she actually prays when she's in the water.

Hamilton's inspiring story will be showcased at the Tribeca Film Festival beginning Friday, April 20. Just last March, she and her husband welcomed their second child, Wesley.