Trust me, otters are nowhere near as rare as the environmentalists make you think. They're everywhere, it's just that humans are usually too loud crashing down the bankside and scare everything away.
If you're fly fishing at night and tip-toeing down a seatrout river in total darkness they'll come right up to you and brush your leg, often calling out wanting a free meal. Blummin' pain they are!!!
Amazing! People only became aware of them on that part of the river when the houses on the road that runs parallel to it started having their garden ponds emptied of Koi and then someone caught the culprits on their CCTV.