Surfer Bethany Hamilton will join Riley Gaines, a former athlete and advocate to protect women’s sports, at a Missouri library on Friday, where the two will promote Gaines’s new children’s book.

The book Gaines and Hamilton will promote, Happy No Snakes Day, teaches “the importance of standing up for the truth.” Hamilton, who survived a shark attack in 2003 before returning to surfing, is one of the growing number of women athletes who have spoken out against transgender athletes competing in women’s sports.