Description Rex the warthog teaches his best friend, Oslo the oxpecker, to swim in this first book in the sweet and funny Level 1 Ready-to-Read series about the unlikely duo. Rex the warthog and Oslo the oxpecker bird are friends who do everything together. But when Rex wants to go swimming, Oslo objects! The water looks cold and wet. There might be sharks. Will Rex be able to help Oslo overcome his fears and join in the fun?