Captain being startled by the sudden appearance of an oil tanker.
Thinking about this, the fella that got told off cos he was supposed to be listening out for oil tankers was the baddie fella who replaced Leading Seaman Steve Arnott, who would otherwise, one would assume, have been listening for oil tankers more effectively if he hadn’t been inconveniently poisoned. So, maybe the implication that he wasn’t very good at the basics of his job was an early clue that there was something not quite right about baddie fella.