Lia Thomas reaches third final at NCAA swimming championships, to be No. 4 seed in 100-yard freestyle

Lia Thomas finishes 4th in 100Y women's freestyle prelim (1:03)

Penn's Lia Thomas finishes with a time of 47.37 seconds to grab the fourth overall spot in the women's 100-yard freestyle prelim. (1:03)

ATLANTA -- Penn swimmer Lia Thomas will be the fourth seed in the 100-yard freestyle final Saturday night after posting a season-best time of 47.37 seconds in the morning prelims at the NCAA women's swimming and diving championships.

Thomas was in seventh after the first 50 but surged into second place in her heat behind Virginia freshman Gretchen Walsh, who touched the wall in 46.78 seconds.

Walsh will be the top seed Saturday night, followed by NC State's Katharine Berkoff, who won her heat in 46.89 seconds. Walsh and Berkoff also squared off in the 100 backstroke Friday night, with Berkoff getting the win while setting American and NCAA records.

Thomas, a fifth-year senior who is a transgender woman, entered the 100 freestyle with the 10th-fastest time in the country, a mark she set at the Ivy League championships in February. She was not considered to be among the favorites in the event.

Yale junior Iszac Henig reached the 100 freestyle final by swimming a career-best 47.55 on Saturday morning and earning the No. 8 seed. Henig, who is a transgender man, is eligible for the women's championships because he has not started hormone therapy.

Thomas and Henig will square off for the first time at the NCAA championships in the 100 freestyle final, though neither is favored to win. It will be a rematch of their showdown at the Ivy League championships, where Thomas got the win over Henig.

On Thursday, Thomas became the first transgender athlete to win a Division I national championship when she won the 500 freestyle. She tied for fifth in the 200 freestyle Friday.

Thomas' victory in the 500 freestyle came amid protests outside of Georgia Tech's McAuley Aquatic Center and noticeable quiet from the otherwise rowdy crowd inside. The protests outside dissipated Saturday, but the mood inside the pool continued to be muted in its reception to Thomas.

Few members of the swimming community have gone on the record with their opinions about Thomas and the inclusion of transgender women in women's sports, but that ice has begun to thaw throughout the championship meet.

For Shelley Hetzer, whose daughter Emily competes in the 200, 500 and 1650 freestyle for Auburn, the fact that Thomas has not won beyond the 500 doesn't affect her opinion on the question of fairness.

"I think it's scientifically unfair," Hetzer told ESPN. "I feel for her, but I think it's unfair for cisgender females."

There is some support mixed in with those who don't feel like Thomas' inclusion in the women's category is fair. Olympic silver medalist Erica Sullivan published an opinion piece in Newsweek on Friday expressing support for Thomas, writing "I can't sit silently by as I see a fellow swimmer's fundamental rights be put up for debate."

In December, Thomas set what was then the nation's fastest times in the 200 and 500 freestyle at the Zippy Invitational in Akron, Ohio. Her success at that meet garnered national attention and upended the swimming season. The NCAA changed its policy for transgender athletes in December, moving from a blanket requirement across all sports to a sport-specific approach that leaned on the policies of the national governing bodies.

But after USA Swimming released an updated policy -- which would have put Thomas' eligibility in jeopardy if applied to the NCAA championships -- the NCAA delayed its implementation, clearing the way for Thomas to compete this week in Atlanta.

When Thomas dives into the pool Saturday night, it will be the final swim of her college career. And the end of a season that has dominated headlines.