Tom Clancy hypothesis on sonar performance...

[Dr.Sid]

Oh I see .. the reflection itself is almost surely too weak to paint anything. In Clancy it is said that pinger can be detected at 5 times range as the echo. That could be even more difference with today's anechoic coatings.
From this you can say that echo is about 5 times weaker then ping.

Also if you wanted to paint anything with your own echo, you would suffer the same pinger's problem .. you would be detected sooner then you get the echo.

Reflection would not be any much directional. Most common reflection comes from curved surface of the boat, and it will act as spherical wave. That means less directional, but also much less energy reflected in any specific direction.

Anyway the ping itself can paint. Yes, sonar use directed beams, but if you look for a target, you look in all directions (omnidirection or rotational id DW's FFG). Only when you track or investigate specific contact you can use narrow beam.

You could skip beaming in direction of your ally, but then you don't know exactly where he is and comunication with sub is always a problem. Also you could tell to the listener 'hey I'm not pinging in this direction, maybe something is there'. Listener could see where you are pinging from amount of reverbation (especially bottom reverbation) from your ping. Reverbation generaly works same way as light beam in fog.