Eat Or Be Eaten.

Information acquisition is almost instantaneous with the use of divine sense. It is not so with the spiritual echo method. There is a delay between the echoes which causes the information to not only be instantaneous, it is also intermittent. 

It makes seeing like being in a dark room and switching on and off a source of light over and over again. So he gets a glimpse of the world before it is plunged into darkness. Then he has to wait patiently for another glimpse. 

The information the spiritual echo brings is also not accurate. The grey water destroys some of the spiritual waves so some information is always missing. The farther the target, the less information is acquired.