"Whereas the minehunters are looking for object detection, we're looking at safe navigation."
The difference is mostly in the data transform applied to the received data. You can in fact do both.
It is a matter of what you feed into the Fourier transform and what convolutional filters you apply to the data. While a sonar (or radar for that matter) that looks for objects will never be fantastic for bottom survey, it may be just good enough and vice versa.
The give-away is in the boxes which do the digital processing. They are nearly always from the same vendor and have the same guts. The difference is mostly in the software load.
Biting the hand that feeds IT
