Many boat and marine electronics just like automobiles use reed sensor and level sensor products to detect position and/or monitor liquid levels.  Below are a few examples.

• Anchor position
• Battery monitoring
• Bilge pump smart sensor
• Clean water supply
• Fuel level sensing
• Gearshift position
• Hatch position
• Kill switch
• Live well monitor
• Oil level
• Out drive position
• Personal beacon device
• Radar antenna sensor
• Reverse osmosis
• Rudder position sensor
• Shore power detection
• Speed indicator
• Toilet Control
• Trim tab position
• Waste level
• Winch level
• Wind speed and direction sensor