crash course

crash dive

An emergency maneuver by a submarine in which it suddenly descends, especially to considerable depth, usually in order to escape an attack or avoid a collision.

due course

Regular or appropriate passage or occurrence

let nature take its course

To permit events to proceed or a situation to develop without intervention or interference.

matter of course

A natural or logical outcome; perforce.

par for the course

To be expected; normal; common.

reverse course

To stop and proceed in the opposite direction.

stay the course

To persist or continue, especially in the face of difficulties.