Uggghhhh this chapter is like sooo old but I'll comment anywayz. I'm think that he or his dad had a bad drinking problem, maybe both because he could have feared his dad was drinking again or since he moved the water so fast to see what it really was he really hoped it was beer for his own personal purpose. Personal experiences lolz...
Surprise update! :D
If it's confusing...it should make sense later in the chapter >__>;; (hopefully hAHAHA...sobbs)
edit: (...i put the wrong onomatopoeia...might change interpretations lmfao sorry;;)