I have seen bass together underwater, especially smallmouth over a rocky hump etc. But they usually show up as a lone fish. Crappie are almost always together and stacked on different levels. One of the reasons they are relatively easy to see in side imaging is that they dont move much until they see something to eat and they are in a group. Pretty much any medium sized fish, grouped up/stacked, especially when relating to some structure is gonna be crappie. Step number one is being on a lake that actually holds crappie.