A helmsman or helm is a person who steers a ship, sailboat, submarine, other type of maritime vessel, or spacecraft. On small vessels, particularly privately owned noncommercial vessels, the functions of skipper and helmsman may be combined in one person. On larger vessels, there is a separate officer of the watch, who is responsible for the safe navigation of the ship and gives orders to the helmsman. In the merchant marine, the person at the helm is usually an able seaman, particularly during ship arrivals, departures, and while maneuvering in restricted waters or other conditions requiring precise steering. An ordinary seaman is commonly restricted to steering in open waters. Moreover, military ships may have a seaman or quartermaster at the helm.