A river or har bor police; customs officers detailed to watch ships in order to prevent smuggling or other violations of law.(noun)
The Century Dictionary (Public Domain)
Use "water-guard" in a sentence
"Always our first business at the end of a day's trek was to ride away and look for the railway station, with its one solitary hut and the half-dozen tents occupied by the water-guard."
"At the depot, he persuaded the water-guard to let him fill his water-bottle, and then, while the"
"Like as not, St. Austell Bay would be patrolled by half a dozen man-of-war's boats in addition to the water-guard: and this meant Dan'l's losing the lugger, losing his life too, maybe, or at the least being made prisoner."