AUSTIN (KXAN) — One St. David’s nurse is giving the gift of life-changing surgeries this holiday season. She is on board the Africa Mercy, the largest privately-owned hospital ship in the world.

“It’s like the wave of an ocean, they come,” said Leesa Sims, of the long lines of patients who gather outside the ship every day.

Sims waited a year to volunteer on board the Africa Mercy, which is currently docked off the coast of Cameroon. More than 400 volunteers from 40 different nations run the ship. They train African health care workers and perform free surgeries.

“I have six cabin mates and one of them is from America,” Sims said. “There’s New Zealand, Canada. There’s Australia. There’s Great Britain, everybody and all age groups.”

Most of the operations are for teens and children living with conditions like large facial tumors, cleft lips and palates and blindness. Sims said the patients notice improvements immediately after surgery.

“Before the natural swelling occurs, you can see [them saying], ‘My lip is put back together,'” she said. “It’s amazing to see their faces. It’s the transformations that we’re here for.”

The intensive care nurse sat on the volunteer waitlist for a year to do a two-month tour. Each volunteer crew member is responsible for paying for their accommodations on board. Sims said she used two months of vacation time from St. David’s South Austin Medical Center to volunteer.

Sims says she’s also learning about illnesses that have been nearly wiped out in the United States.

“Most of the things that we see here were taken care of when children in America and Great Britain were babies,” said Sims. “So, to see these conditions and to see how they’re treated medically…this hospital has taught me a lot, daily.”

Sims flew to Cameroon and boarded the ship just before Halloween. She missed the Thanksgiving holiday with her family. And, she was absent from her daughter’s 30th birthday celebration. But, she said the reward for volunteering on the Africa Mercy is almost impossible to get in the states.

“It’s humbling to come here. Poverty is worldwide,” she said. “And, to see people who can still smile and find joy in their everyday life…that’s what I try to take back.” Sims returns next week.

The Mercy Ship typically sees nearly 2,000 surgical patients and about 8,500 dental patients every year. The supplies and equipment on board the ship are paid for by worldwide donations.