The Boy who Wouldn't Swim by Deb Lucke

From chapters.ca:
Come on in! The water's fine. Electric, sherbet-y colours, uniquely comic characters, and a story line filled with high comedy mark this fabulous picture book by new talent Deb Lucke. Eric Dooley just won't swim. If sweating in the hot summer sun while everyone else cools off in the pool isn't bad enough, Eric's younger sister is having the time of her life. When he sees her dog- paddling right across the middle of the pool, under his sunblock he''s positively green with envy. Not to mention sweaty. And irritated. But after the babies in the wading pool give him dirty looks for invading their territory, Eric finds a way to conquer his fears. And just like that he goes from being the boy who wouldn't swim...to being the boy who won't get out of the pool. Not even in October.