Just for giggles, I Google Mapped the area. While technically true, there’s no way a monster could make it. Heading for Morey Firth, there’s quite a bottleneck at 57.432299, -4.301450 (google maps). Here’s a drones view of that section.
The western branch is blocked by a lock and the east side is split into shallows.
On the southern end, the lower of the two outlets is blocked by locks (57.144733, -4.683086) and RIVER OICH proper is mostly Grade 2 rapids.
One incredibly fun fact is that if you put the Loch Ness in the middle of your screen (Google Maps), the little Street View guy turns into the Loch Ness Monster.
Yep, I’m not much fun at parties.
:~)