The antagonist sits out in the open on a day cold enough to keep a frozen lake from melting without protection for his face. Frostbite would have set in within 30 minutes to an hour and made the scenario he was trying to stage implausible to anyone who examined the scene.
There would have only been one set of footprints leading from the dive site on the pond and they wouldn't have been the protagonist's. If when her body was discovered, there would have been no explanation for her getting to the pond without being carried.