"We met so many families along the way who either lost someone or are currently going through it," said San Clemente resident Gail Lopez. "So just to do something for them."
What she is doing is swimming, biking and running in this weekend's Nautica Malibu Triathlon.
"I just actually reached my goal this morning. Someone donated $1,000 last night," said Lopez.
Lopez wants to support Children's Hospital Los Angeles, as it was instrumental in helping her 13-year-old daughter, Kate, through her battle with osteosarcoma, a rare form of bone cancer.
Redondo Beach resident Cole Stecyk and parents are participating for younger brother Chase, who died last year from a rare form of cancer.
"I'm doing it in honor of my brother," said Stecyk.
Stecyk is motivated by a memory of hiking with Chase, who was intent on climbing a mountaintop even after painful chemotherapy.
The Stecyk family raised $20,000 for a machine that helps many hospitalized kids.
"We actually bought a bladder scanner for the hospital so children do not have to have a catheter inserted into them because that's really uncomfortable," said Stecyk.
Then there's Palm Desert resident Bill Bell, who motivates in a different way.
"This is my 90th year, I am racing at 90," said Bell. "They had to put a new group in."
Bell knows of three other racers over 90, but they are East Coasters, so he is sure to win his division. But that's not why he does it.
"God gave you this great body, you take care of it," said Bell. His motto: "Use it or lose it."
"I use the theory of, you take a lawnmower, you put it out on the lawn, you leave it out in the rain, it gets rusty. Same with your body," said Bell.
More than 5,000 are registered to do the half-mile swim, 18-mile cycle and 4-mile run. The fun begins on Saturday with a sand castle contest, fitness clinics and entry packet pick-up.
The classic race starts around 7:15 a.m. Sunday, but you should arrive at the crack of dawn to get a good cheering spot and parking space, because both are at a premium. Zuma Beach opens at 4:30 a.m.