Kathryn Prescott suffered a hypothermic shock while filming the lake scene. Filming took place in the middle of November, when the water was really cold at the time. Right after she jumped in the water, she had a panic attack and couldn't breathe properly, which caused her to climb out of water instinctively. However, while in the water, she was still able to deliver her line, albeit in an extremely squeaky voice due to her reaction. Her line and the moment she's climbing out made it into the finished episode. After that, she was treated by paramedics. Further scenes at the lake were planned, including one in whuch Emily and Naomi are playing around in the water, but they were not filmed because of that incident.