Dark waters

After the death of her father, a beautiful Londoner travels to a desolate island to investigate the dead man's bequest of a large sum of money to be paid annually to the reclusive nuns of a local convent. Given little information by the secretive sisterhood, Elizabeth strikes out on her own with the aid of a helpful novice. They discover the convent serves as a prison for an ancient aquatic demon whose awful wrath is held at bay only so long as t...