Automatic bilge pumps serve a noble purpose - to remove water from a boat's bilge (lowest point in the boat, below the waterline) which can come from water splashed over the rails, rain, slow leaks, or simple condensation over time.

On the other hand, an automatic bilge pump will pump out not only water, but any other fluid happening to find its way to the bilge: fuel, antifreeze, oil, or such unfortunate substances as the contents of the sewage holding tank, should an accident occur.

The environmental consequences of pumping the wrong fluid overboard are subject to any number of laws and simple human decency. But the pump has no idea, it just reacts to fluid level by turning on and pumping.

So what I propose is a fairly rudimentary sensor to detect the contents of what is being pumped overboard (by pH, density, optical transmission, any number of techiques) to restrict pumping to pure or salt water.

This works even if the bilge is full of oil and the boat springs a leak - the oil rises above the water, and the pump quits pumping only when the water is removed, but before pumping out the oil.

Accepting boat-shaped bread (or perhaps life-ring shaped bread is more appropriate!) at your discretion. Help prevent fishbones!