A hot-water-heater heating element is extremely attainable. But can very likely be improved upon. Needs to have someway to keep corrosion off the copper. Salty water is great for turning orange copper green.
Not in the time we'd be using it for. We just need to go 500'. We don't have the capacity to come up with a copper alloy that won't rust in salt, or a chemical that will protect it. Our task is to simply demonstrate feasiblity, cheaply, and then let the boys with the big dollars build the actual probe.
