Why did William Dampier bring his ship ashore for ten weeks in Roebuck Bay?

To repair it. As an experienced sea captain and pirate, Dampier became the first Englishman to explore and map parts of New Holland and New Guinea. On 4 January 1688, his ship the 'Cygnet' was beached on the northwest coast of Australia, at King Sound near Buccaneer Archipelago on the north-west coast of Australia. While the ship was being repaired Dampier made notes on the fauna and flora he found there.