I guess this brook is rather narrow in places, less than two meters, and looks quite deceiving as nobody who has ever accidentally entered the waters has survived the ordeal. Evidently the water is deep, with a fast current that swirls into severe undercuts and underground chambers. Where I live we have irrigation canals that look inviting, but are swift and deadly just below the surface.
While I don't wish to make light of this otherwise tranquil body of water which has taken far too many lives, the idea of a hidden danger struck home for this GM. I had to drawn a map of my version of the Strid, renamed the Strix. The locals know well enough to give the brook a wide berth, only traversing the water safely over one of the few bridges across. So deadly has this brook been that is forms a natural border between two counties.
The second map is just an overlay of the caverns and tunnels beneath the fields.
Here are the links for the two maps:
If you find either one of these useful, please let me know.