Audio problem: When Chelsea is screaming "Liar! Liar! Liaar!!" to her mother, Kathy, in one shot we see Chelsea's mouth still saying "liar," but no audio is heard. (00:47:05)
Audio problem: When the realtor suggests turning the basement into "A game room. Or a play room," her mouth says otherwise. (00:09:20)
Answer: He sees the balloon, and instantly assumes his step-daughter is inside the boat house, and hence is in danger of slipping and drowning (or perhaps already in such a situation). He rushes straight out to get there as quickly as possible. Checking her room, or telling his wife would take up time, not to mention he is probably running on adrenaline.