Submarine Command Course

The fourth phase is the assessment, during which the candidates (of which the maximum is six) show their ability to command a submarine unaided during war-like conditions.

[4] However high attrition rates during the war meant this training could not always be passed on, and the less experienced submarine commanders were in turn more likely to make errors resulting in their death and the loss of the boat.

Following World War II, the Royal Netherlands Navy began to send officers to the course.

[4][6] The second stage, known as COCKEX (a corruption of the old COQC name plus the standard shorthand for exercise), takes the candidates to sea, where they practise the skills learned in the simulators, along with tactical safety training.

[6] One example of the type of exercise, from the 2004 course, required the candidate to take their submarine into a harbour (simulating a naval base) to lay mines, with less than 6 metres (20 ft) of clearance between the fin and ferries passing overhead, and even less distance between the keel and the harbour floor, while a warship used active sonar to hunt for the submarine.

[4][6] According to Commander Marc Elsensohn, Teacher for the 2004 diesel-electric course, the main reasons for failing are that the candidate regularly loses situational awareness, or shows a narrow focus or over-reliance on one tool or aspect of operations.

A failure on Perisher means that the unsuccessful candidate is not permitted to return to sea as a member of the Submarine Service (although they are still allowed to wear the dolphin badge).