A nautical instrument that can be repetitively mounted and removed from a surface within a ship without the use of tools or other instruments. The nautical instrument incorporates a mounting system that achieves slidable locking engagement of the nautical instrument to a bulkhead plate that is permanently secured to the surface of the ship. In another aspect, the invention is a nautical instrument that is extremely resilient to corrosion and harsh weather environments. In one embodiment, the invention is a nautical instrument comprising: a housing having a front face comprising an opening, the housing constructed of a material coated with zirconium; a transparent lens hermetically enclosing the opening of the housing; and a gauge mechanism for measuring a desired standard, the gauge mechanism positioned within the housing.