The couple were in a boat on a shallow part of the lake when the woman decided she wanted to walk back to shore , said Utah County Sheriff's Sgt. Spencer Cannon.
"The water wasn't too deep where she got out but it was a little difficult to navigate," Cannon said.
Around 8:30 p.m. search and rescue crews along with Life Flight were called to the scene to help search for the woman through the reeds.
They were able to locate the woman a few hours later.
The woman has not been identified at this time.