Unfortunately, the western portion of the Scottish coast is extremely rocky. The Covenant runs up against a hidden reef and sinks. Davie is thrown from the ship by a wave and winds up washed ashore on the barren island of Earraid. (Here, we definitely suggest that you consider consulting a map.) Davie suffers from hunger and thirst and all-around sickness for a while before discovering that the island he's on is only an island at high tide. When the tide goes out, you can walk to the next island over, the island of Mull, which Davie does.