Sijbrant Janszoon Mol commanded a hired merchantman, the Witte Olifant (28 guns). This was apparently a hired Italian ship named the Elefante Bianco in mercantile service. In August 1653, he was in Anthonis van Zalingen's squadron off of Livorno, blockading Henry Appleton's squadron. . The van de Velde drawing of the Battle of Livorno shows the taffrail with a large elephant. His ship was part of a 16-ship fleet commanded by Johan van Galen, who flew his flag on the Amsterdam ship Veerenigde Provinciën (40 guns). In the Battle of Livorno on 14 March 1653, Henry Appleton led his squadron out of the harbor at Livorno prematurely, and was faced with the entire Dutch fleet present. Appleton quickly lost the Bonaventure (44 guns) to an explosion with only 5 survivors. Almost immediately, Van Galen lost a leg and eventually died. Of the ships in Appleton's squadron, only the fast Mary escaped. The Sampson was destroyed by a fireship, while the Peregrine and Levant Merchant were taken. Appleton's flagship, the Leopard (48 guns) was overwhelmed and taken, as well. The only Dutch loss was the hired merchantman Madonna della Vigna, which was forced ashored north of the harbor. Richard Badiley's squadron exchanged fire with the 8 ships, including the Witte Olifant, and then withdrew, eventually from the Mediterranean Sea. That left the Dutch in control, and allowed them to send ships home.
In 1658, the city of Amsterdam fitted out two merchant ships for the war against Sweden (as per Jan Glete). They were the Waeg and the Cogge, both of 40 guns. The Waeg had a crew of 107 sailors and 30 soldiers. The Waeg was commanded by Sijbrant Janszoon Mol, and was assigned to Lt.-Admiral van Wassenaer's division. He took part in the Battle of the Sound, where the Dutch soundly defeated the Swedish fleet, with the loss of Witte de With and his flagship Brederode, which had run aground and been severely raked.