Hi @cavediver, welcome to the forum 
Both the Ping Sonar Altimeter and Echosounder, or the Ping360 Scanning Imaging Sonar are designed and set up to work as distance sensors, so they only measure the intensity of the returned sound. That means there’s no frequency information available from which to calculate a doppler shift, so velocity calculations can only be done with changing position data.
Assuming you’re always going towards a wall, or at least something detectable that has a known relative position (to you, possibly from a reading performed while you and the target are stationary) and known absolute velocity (in the ocean reference frame) this could potentially work, but you’d have to write the code to calculate velocity yourself. I’d imagine you’re likely better off using a doppler velocity log (DVL), or an accurate inertial measurement unit (IMU) or underwater GPS.