High-contrast capillary depth gauge and watch comprising such a depth gauge

The gauge (1) has a capillary tube of triangular section that is arranged against a background opposite to an observation surface and visible by transparency from the observation surface. A tubular section is filled with water and a reflection surface is visible by reflection from the observation surface. The capillary tube forms an isosceles triangle whose equal angles having an angular value between 48-60[deg] . The reflection surface is arranged opposite on the sides of isosceles triangle. An independent claim is included for watch.