An image display system comprising a position information obtaining device obtaining position information of a ship, an information storage device storing an electronic marine chart including seafloor shapes and a tide table, an image display device provided at the ship, an image providing device providing an image to the image display device, and a direction obtaining device obtaining the direction of the ship, the image display device being provided with a transmissive-type display for allowing to see a view therethrough, and wherein the image providing device is adapted to obtain a depth below sea level at a position of the ship based on the position information of the ship obtained in the position information obtaining device, the tide table, and information related to depths indicated on the electronic marine chart, create a first virtual space image of a seafloor shape below sea level at the depth at the position of the ship based on the position information of the ship, the obtained depth below sea level, and seafloor topography image data indicated on the electronic marine chart, determine a visual field from the transmissive-type display based on position information of the image display device determined based on the position information of the ship obtained in the position information obtaining device, the direction obtained in the direction obtaining device, and a size of the transmissive-type display, create a third virtual space image of the view point from the transmissive-type display, of the seafloor shape below sea level at the depth within the visual field by performing coordinate conversion of the first virtual space image into a second virtual space image of the view point from the transmissive-type display, of the seafloor shape below sea level at the depth, and extracting the third virtual space image within the visual field from the second virtual space image based on the determined visual field, and provide the third virtual space image to the image display device, wherein the image display device is adapted to display the third virtual space image of the seafloor shape provided by the image providing device in a manner overlaid on a view from the transmissive-type display of the image display device. wherein the image providing device is adapted to obtain a depth below sea level at a position of the ship based on the position information of the ship obtained in the position information obtaining device, the tide table, and information related to depths indicated on the electronic marine chart, create a first virtual space image of a seafloor shape below sea level at the depth at the position of the ship based on the position information of the ship, the obtained depth below sea level, and seafloor topography image data indicated on the electronic marine chart, determine a visual field from the transmissive-type display based on position information of the image display device determined based on the position information of the ship obtained in the position information obtaining device, the direction obtained in the direction obtaining device, and a size of the transmissive-type display, create a third virtual space image of the view point from the transmissive-type display, of the seafloor shape below sea level at the depth within the visual field by performing coordinate conversion of the first virtual space image into a second virtual space image of the view point from the transmissive-type display, of the seafloor shape below sea level at the depth, and extracting the third virtual space image within the visual field from the second virtual space image based on the determined visual field, and provide the third virtual space image to the image display device, obtain a depth below sea level at a position of the ship based on the position information of the ship obtained in the position information obtaining device, the tide table, and information related to depths indicated on the electronic marine chart, create a first virtual space image of a seafloor shape below sea level at the depth at the position of the ship based on the position information of the ship, the obtained depth below sea level, and seafloor topography image data indicated on the electronic marine chart, determine a visual field from the transmissive-type display based on position information of the image display device determined based on the position information of the ship obtained in the position information obtaining device, the direction obtained in the direction obtaining device, and a size of the transmissive-type display, create a third virtual space image of the view point from the transmissive-type display, of the seafloor shape below sea level at the depth within the visual field by performing coordinate conversion of the first virtual space image into a second virtual space image of the view point from the transmissive-type display, of the seafloor shape below sea level at the depth, and extracting the third virtual space image within the visual field from the second virtual space image based on the determined visual field, and provide the third virtual space image to the image display device, wherein the image display device is adapted to display the third virtual space image of the seafloor shape provided by the image providing device in a manner overlaid on a view from the transmissive-type display of the image display device.