Why did Gulliver get marooned?

The real problems begin in 1699. Gulliver sets sail on a voyage that starts out prosperously but quickly takes a turn for the worse. The ship encounters violent storms, has bad food, and weakens the crew (twelve crew members die) when the ship hits a rock and is split. Six of the crew members, including Gulliver, get into a small boat and row until they are overturned by a "sudden Flurry." Gulliver swims until he is nearly exhausted, at which point he finds an island, comes across a patch of grass, and sleeps for what he estimates is more than nine hours.