I would prefer that they only target empty tankers, and shoot them to disable them, not to sink them.
Full tankers make an environmental mess it they are holed.
Hit the engine room only, and cause them to be out of commission for a year or two. And target the cargo after it has been unloaded and is on land in the oil terminal tank farm, which is what they have been doing.
At the tank farm they have enclosures around the tanks to contain a spill.