Zac Efron, James Marsden, and Luke Hemsworth were among the super-fit hunks who took part in the Nautica Malibu Triathlon on Sunday morning (17Sep17).

Baywatch star Efron also competed in the Zuma Beach challenge for Children’s Hospital Los Angeles last year (16).

Joined by his brother Dylan, Zac posted a shot of himself and other competitors on Instagram, adding the caption: "We raced our hearts out for @childrensla."

Funnyman Joel McHale, Cassandra Scerbo, Isabelle Fuhrman, Beverly Mitchell, and former Two and a Half Men star Jon Cryer also took part.

Zac and Dylan also visited patients at the hospital on Sunday.

"Huge thanks to @zacefron for visiting our Children’s Center for Cancer and Blood Diseases unit - and for raising awareness and funds for CHLA’s pediatric cancer research program! We’ll see you at #NauticaMalibuTri," a hospital spokesman wrote on Instagram.