In the beginning of the story Sully and scoot who are siblings were out on the sea dog for Scoot's birthday.
Then all of a sudden a huge wave called a rogue wave came and crashed the seadog taking Scoot (the younger sister) down with it.
Scoot was knocked unconscious with a limited supply of air in a dock of the seadog, she was thinking that she was going to die.
Sully noticed Scoot was down there and went to go rescue her trying to break her out, but he couldn't pry it open and he was thinking the worst possible scenario
Once Scoot and Sully finally found a way to get her out with the clapping technique they came above sea level and meet some people who helped them get back to shore.
Even though the seadog went down underwater it still "did it's job" in getting its people to safety, without that air-pocket who knows what would of happened to Scoot. The good thing is that both Scoot and Sully made it out alive.