I'm not sure I understand your question. PM claimed they couldn't find a long stretch of road in their locale to test the maximum distance the detectors had. So they used 2 boats on water, one with a radar gun and one with the detectors.How did you test a boat?
This is pointless as it doesn't equate to highway driving. Radar is going to travel differently on water than it will on asphalt roads, bridges, etc..