This page of the Dying Light 2 guide lists all the inhibitors available in the wasteland.
Inhibitor no. 1
Important nearby locations: Dam
Quest: not applicable
To reach this inhibitor you must dive down and swim to the very bottom of the river. Remember that Aiden's stamina determines how long he can breathe underwater. You'll find more information regarding this mechanic on the page: Stamina - how to restore?