The 'Water Girl' (or 'Mermaid') is a mysterious, hostile entity encountered in the underwater sections. She is a significant environmental threat, capable of grabbing and drowning the boy if he gets too close. Her 'boss' encounters are less about direct confrontation and more about navigating her patrol patterns, using submerged objects for cover, and manipulating water currents to avoid her. Later, you'll gain an ability that allows you to temporarily stun her, creating brief windows for safe passage. Understanding her movement and attack range is vital.
