The experienced helmsman uses measured responses to sea conditions, even when encountering heavy weather that may cause a ship to pitch and roll as it pounds its way through oncoming waves. Subsequently, the helmsman learns to relax and take into account the vessel's natural rhythm in order to avoid oversteering whatever the maritime environment. Consequently, more accurate steering is attained with less rudder. Applying the minimal rudder required to steer a course reduces drag of the ship, thereby favorably impacting the ship's speed and operating costs. One of the helmsman's most important duties is steering a ship in a harbor or seaport when reduced speeds slow a ship's response to the rudder. For it is during ship arrivals and departures, when most ship collisions or groundings occur. Clear communication, then, between the officer of the bridge and the helmsman is essential for safe operations. The officer or harbor pilot relies upon the helmsman to flawlessly execute steering commands to avoid a variety of hazards, including man-made obstacles, land formations, grounding in shallow waters, and the threat of collision with other vessels. In addition, powerful sea tides and river currents encountered in seaports heighten navigation dangers, as a ship's ability to stop is severely limited. Relieving the helm Helmsmen of merchant and military ships that are underway stand watch at the helm for a set period of time before being relieved by another watchstander. The person being relieved will complete any course change or other critical maneuver that is in progress before handing over the helm. Merchant vessels The helmsman handing over the helm will inform the relief helmsman of any rudder commands in place and pertinent conditions. "Steering 180. We have oncoming traffic two points on the starboard" for example. In addition, the current helmsman should inform the relief if there are any peculiarities affecting steerage. Similarly, the helmsman will also point out if he or she is steering on a landmark, range, or navigational light. The relief helmsman is obligated to repeat the course being steered or other rudder command in order to demonstrate an understanding of the situation at the helm. On merchant ships, it is taught at the various maritime academies that the proper way to relieve the helm is for the helmsman being relieved to call out loudly the ship's course per gyro, course per standard magnetic compass, steering mode, rudder angle, and the pump the