They wanted to compel Captain Phips to turn pirate.

There was a much better prospect, they thought, of growing rich by plundering vessels which still sailed in the sea than by seeking for a ship that had lain beneath the waves full half a century.

They broke out in open mutiny; but were finally mastered by Phips, and compelled to obey his orders.

It would have been dangerous, however, to continue much longer at sea with such a crew of mutinous sailors; and, besides, the Rose Algier was leaky and unseaworthy.

So Captain Phips judged it best to return to England.
Before leaving the West Indies, he met with a Spaniard, an old man, who remembered the wreck of the Spanish ship, and gave him directions how to find the very spot.