while it looks round from the information so far, the resolution of the sonar image was not high enough to verify that it is indeed round.

Sea Bat 7125-e - High resolution multi beam sonar, the S410 Deepwater hydrographic and broadband echosounder, and the PDS2000 Software package.

The very strong property of the synthetic array sonar is the ability to acquire a high azimuth resolution from a physically small array.