Drinking only sweat would lead to dehydration like seawater, and coprophagia would cause infections and rapid health decline due to toxins and lack of nutrients.I hope the protagonist can have a story about eating. When he's hungry, he eats girls' feces, and when he's thirsty, he drinks girls' foot sweat.
Not kink shaming—just saying, if that became the PC's source of fluids and nutrients, immersion would break fast.