Warships have a lot of extra bulkheads to make a hit survible. We ran drills 4 to 5 days a week on how to stop the water from coming in and make the repairs to keep us combat ready. While the tanker does have a double hull (at least the newer one do), the cargo is extremely flamable. It makes a very good boom. Depending on what hits it, it could literally disappear, or take hours to sink if at all.
Former sub sailor.