Final answer:
Ernesto's water party was probably interrupted by a practical matter needing adult intervention, like a plumbing issue that demanded immediate cleanup.
Step-by-step explanation:
Ernesto's water party was most likely interrupted by a situation that called for practical adult intervention—such as a plumbing issue or a mess that required immediate attention. This is suggested by the references to calling a landlord for household issues and the event in which a character's bath is transformed into a delightful experience, only to have it interrupted. In literature, such interruptions often serve to transition from a state of leisure to one demanding action or responsibility.