Richmal Crompton 
William — The Fourth [EPUB ebook] 

There is only one William. The loveable imp and his band of Outlaws have been harassing his unfortunate family and delighting hundreds of thousands of readers for years. Here, William invents a water race where competitors have to run with a mouth full of water, without swallowing it or spitting it out. It’s just a shame he doesn’t have time to think before speaking to (and drenching!) Mrs. Adolphus Crane during the race! (Goodreads)