A marine vessel equipped with a countermeasure system having a substantially vertical launch tube that is at least generally rotatable about a vertical reference axis that extends through and along a length of the launch tube. This rotation capability of the launch tube may be used to affect an aiming of an associated countermeasure cartridge at least generally disposed therein. One or both the launch tube and countermeasure cartridge of this countermeasure system are generally equipped with a rotation inhibitor for substantially preventing independent rotation of the countermeasure cartridge relative to the launch tube at least when the countermeasure cartridge is disposed within the launch tube. The present invention is also designed to enable the associated countermeasure cartridge to be pitched over to a predetermined pitch angle (relative to the reference axis of the launch tube) to affect a desired flight path after launch of the countermeasure cartridge.