Set free, he supported his mother and three sisters by working in a Rotterdam shipyard. Tromp went to sea again at 19, briefly working for the navy, but he was captured again in 1621 after having rejoined the merchant fleet, this time by Barbary corsairs off Tunis. He was kept as a slave until the age of 24 and by then had so impressed the Bey of Tunis and the corsair John Ward with his skills in gunnery and navigation that the latter offered him a position in his fleet. When Tromp refused, the Bey was even more impressed by this show of character and allowed him to leave as a free man.