Paramedics attempted to provide CPR at the scene, then rushed the girl to a hospital, but she was unable to be resuscitated.
It also comes two months after the couple revealed that they were expecting their third child together.
"We are beyond devastated", Miller posted on his Instagram account Monday night. "Our baby girl, Emmy, passed away yesterday", the family wrote on Instagram, along with photos of their blond-haired baby girl.
"We definitely get at least one child a year who drowns in a pool", Beyrer told The Post.
'Her love, her light, her spirit will never be forgotten'.
Emmy was the youngest of Miller's four children; he has two sons and another daughter. He also shared a picture of his baby girl sitting on his lap.
He married professional beach volleyball player Morgan Beck in 2012.
Carrie Braun, a spokeswoman for the Orange County Sheriff's Office confirmed the death was under investigation.
Bode and Morgan are now expecting another child.
Emeline Grier Miller was born on November 5, 2016.
Miller is a decorated USA skier who has earned six Olympic medals over three Games in Salt Lake City (2002), Vancouver (2010), and Sochi (2014).
He won six medals in the Winter Olympics throughout his career, the most of any USA skier.