1. A display device for installation in a ship, comprising: a detector that detects a touch operation; an image acquirer, associated with the display device, that acquires at least two of a navigation image containing map or nautical chart information created based on information obtained from a GNSS sensor for detecting a location of the ship, an underwater detection image created based on information obtained from an ultrasonic transducer for detecting underwater directly under the ship, and a radar image obtained from a radar antenna for detecting a location of an object around the ship; a display unit that displays acquired images in respective divided areas of a display screen; a processor executing a gesture detector that detects a predetermined touch gesture based on the touch operation detected by the detector, an operated location detector that detects an operated location of the touch gesture, and a divided area identifier that identifies which image among the images is displayed in the divided area corresponding to the operated location detected by the operated location detector; an image processor having a function to perform scrolling or zooming of the display screen corresponding to the touch gesture, and for changing a direction or a motion range according to the image being displayed in the identified divided area, upon performing the scrolling or zooming, wherein the image processor applies a limitation to scrolling or zooming based on the identified image corresponding to the operated location of the touch gesture; and wherein the image processor does not fix the direction of scrolling or zooming when the image in the identified divided area is the navigation image, and fixes zooming to a one dimensional zoom direction when the image in the identified divided area is the underwater detection image.