... Using depth to tell where you are is really only
useful if your running out of water....

Given a working GPS and a WGS correctable chart that may be true.
Those of us who need to work our pilotage in places without GPS
correctable charts still find echo sounders useful tools for
navigation at times. These days this is kind of a specialized use
and as long as you know how the sounder was calibrated it is easy to
do any needed instrument corrections in your head. In the "old days"
when LORAN and RADAR were rare on small boats we used echo sounders
for navigation all the time even in pretty deep water.

-- Tom.