Hi; I hope you don't mind this rather long comment on the subject?
Bunker Fuel at the Pressures and Temperatures down there poses No problem. When the ship is gone the oil will get covered by sand and silt and be discovered a thousand years from now as a rare find of Fossil Fuel!
The Oil we carried on The Shell Orion had to be kept warm or it would turn into a very viscous sludge or worse. That's why when a tanker wrecks it's such a mess. If we let it thicken we'd have to wait probably weeks to unload.
They still find Globs of the Stuff in Prince William Sound. BUT, according to the Native Americans there, the Globs have been brought up since BEFORE the White Man EVER showed up. It's a Natural Oil Seep!
We had a flying Spotter when we worked on The "Cape Mohican Oil Spill" in S.F.Bay.What he didn't understand, LORI Ladder brushes could not Pick Up or Skim Diesel Fuel! We could pick up the thicker stuff cause that's what the gear was for.
He had Us chasing Rainbows (For Real) Caused by Diesel Fuel which Dissipates in a short time but when it is spilled in water it creates a thin film that Aerosolizes quickly then is gone with the Breeze. Oh! That doesn't mean it's safe. No Pollutant is safe!
Somebody asked once ," Why do you guys wear Moonsuits when you go after that stuff"? Well it is a good question. All the heavier and some of the lighter product give off gasses after being processed in a refinery. I guess its because of what is mixed in to create the specific product. Some of that stuff not only kills by coating wildlife but, also by emitting gasses once exposed in the environment, that can kill too.
That's why you'll see a skimmer Company working in a close in area also has a crewmember sticking out their arm, At the bow of a small LCVP type boat, whose hand is holding a Dreager Measuring device as they nose into the grasses and trees along the shore. It measures the amount of Volatile and Non - Volitile organic compounds in the air in and around, the spill area near the Water's surface up to six to ten foot above the water. No, It doesn't usually go higher because it consists of heavier molecules. But Wind and Breeze will dissipate it over a short time sometimes. I have heard of "Pools" of gas formed when there is a small clearing surrounded by taller plants!