PURPOSE: To display various information by accommodating in a display accommodating case an optical image display means having a display surface for displaying the information and an optical member for projecting information display light emitted from the display surface toward the inside surface of a transparent plate.

CONSTITUTION: A display accommodating case 3 is fixed to a hydroscope body consisting of an eyeglass frame 1 and a window 2 formed of transparent plates 2a, 2b connected to the eyeglass frame 1 in the water-tight manner. In the display accommodating case 3, are accommodated an optical image display means D having a display surface D1 for optically displaying information and an optical member A for projecting information display light L emitted from the display surface D1 toward the inside surface of a transparent plate 2a. Thus, various information can be displayed to a wearer of the hydroscope so that he can visually perceive the information.