Abstract: In a first aspect, the subject invention provides a variable-intensity light emitting diode (LED) module which includes: a first LED string having first and second ends, the first end being connected to a positive voltage terminal which is connectable to a positive voltage input of a direct current voltage source; a first terminal connected to a first resistor which is connected to the second end of the first LED string; and, a second terminal connected to a second resistor which is connected to the second end of the first LED string. The first and second resistors have different resistances. A negative voltage input of the direct current voltage source is selectively connectable to one of the first and second terminals, whereby, the intensity of light generated by the first LED string is determined by which of the first and second terminals is connected to the negative voltage input.

Abstract: The depth of water ahead of a vessel is detected by sonar means carried aboard a drone stationed by radio control ahead of the vessel. Detected depth information is transmitted from the drone to the vessel where it is displayed for use by the vessel pilot in navigating shallow waters.