Complex sentence: That night, Tina runs to the dock alone while grieving her father, sensing a presence in the lake and mistaking it for him, she inadvertently releases a badly decayed Jason from his underwater prison.
Split into simpler sentences: That night, Tina runs to the dock alone while grieving her father. Sensing a presence in the lake and mistaking it for him, she inadvertently releases a badly decayed Jason from his underwater prison.