Here's what I think is driving this:
The "OLD SCHOOL" bilge switches had mercury switches in them. Two electrodes within the float body made a circuit when the liquid mercury contacted them during of the "up' position of the buoyant float. However, mercury is a heavy metal, is poisonous, and accumulates in the body, just like lead and most heavy metals. The safe disposal and recycling of used mercury devices is the real driving issue.
Environmental concerns have pressed for the elimination of mercury, and more recent designs of bilge switches/floats have used metal balls in substitution for liquid mercury. These are more problematic and have reliability issues.
This new type switch has already been used before, where exposed electrodes test for the presence of water by testing for conductivity. The new version probably has an integrated circuit chip /"brain" incorporated into it. The older versions wee fairly expensive, and didn't see much use, very possibly because of reliability issues. I suspect they get pretty gunked up with oil, hair, fish scales, salt, and other miscellaneous lost and found goodies.
I'd be willing to bet these new switches (and the pumps that use them) will make us long for the good old days.
Does anyone have some good old mercury bilge pump switches to sell???
Joe. :teeth :thup