The Dragon Raft, by Rory Barnes (epub/Kindle.pdf)
Wal is a dreamer: he imagines escaping from his parents by building a raft. His friend Billy is more practical. Together, they construct a makeshift craft, and sail it along the local sea coast. But Wal still dreams of adventure, and one dark night he sails into the teeth of a growing storm. In the wild hours that follow, he must find the strength to persevere—and survive!
A great tale of storm and sea!