What Song?

This man wrote a famous song. Any idea what it was?

Born in London July 24, 1725, the son of a commander of a merchant ship which sailed the Mediterranean. In July or 1732, thirteen days before his seventh birthday, death took his saintly mother who had since his third birthday been his teacher and friend. He took the death of his mother hard. In fact, it became evident that he was bitter at God over his circumstance because he began as one author puts it, "a decline into rebellion and degradation that lasted until his 24th year." At 11 years of age he went to sea with his father and made six voyages with him before his father retired. In 1744 he was forced into service on a man-of-war, the H. M. S. Harwich. The conditions on board were intolerable to him, so he deserted but was soon recaptured and publicly flogged and demoted from midshipman to common seaman.

Finally, at his own request, he was exchanged into service on a slave ship, which took him to the coast of Sierra Leone. He then became the servant of a slave trader and was brutally abused. Early in 1748 he was rescued by a sea captain who had known his father.

He ultimately became captain of his own slave ship. And what kind of captain was he? It is reported that at times he was so wretched that even his crew regarded him as little more than an animal. Once he fell overboard and his ship's crew refused to drop a boat to him. Instead they threw a harpoon at him, with which they dragged him back into the ship.

(This isn't my writing, I copied & pasted it, but what famous song did this man write?)