[Aktungbby]

Revenant342! What has been overlooked is 'in ballast'; even when empty of petroleum products, an empty tanker has any amount of water taken aboard to compensate to stabilize the vessel in transit empty of a 'payload'. This actually causes much eco-damage in the world today when it is dumped. A tanker ''in ballast' full of water is hard to sink. Many U-boat commanders claimed tonnage from in ballast tankers that survived torpedo attacks from being in ballast. One such was the Kittanning, struck three times in one attack and surviving until 1965

The Kittanning (Master Raymond J.S. Chambers) had left port at 13.30 hours, but soon thereafter the third assistant engineer fell and seriously injured himself and the master decided to return to Cristobal. At 16.31 hours, just after the ship changed course back at 14.5 knots, a torpedo struck on the starboard side at the #6 tank. At 16.46 hours, a second torpedo hit the #7 tank on the same side abaft the midships house and the ship swung hard right. The explosions opened a hole 65 feet long and 20 feet high and flooded five tanks, causing a 35° list to starboard. At 17.00 hours, the ten officers, 39 crewmen and 25 armed guards (the ship was armed with one 5in, one 3in and eight 20mm guns) abandoned ship in four lifeboats, but two boats swamped in the choppy seas and squally weather. A coup de grâce, fired at 17.06 hours, struck on the port side at the #4 tank under the midship house, causing the tanker to right herself and float on an even keel. The U-boat had reported another torpedo fired at 18.49 hours, but it seems that it had missed.

In short, in SHV at least, the tankers are miserably hard to sink. I'm not sure about the realistic 'ballast' programming, but I look for easier prey.