Your vessel has run aground and upon taking fuel oil tank soundings, you find that a fuel tank level has increased. You therefore should suspect __________.

Correct Answer: Option D — a crack in the hull portion of the fuel tank

An unexplained increase in a fuel oil tank's level following a grounding strongly indicates that the hull shell plating forming the tank boundary has cracked, allowing higher-density surrounding seawater to enter and displace or mix with the fuel.