I think at the first post you can see some bubbles created by an ships-engine. A bypassing ship puts lots of very small bubbles into the water, which really take some time to drift to the surface. On th 2nd and 3rd You've just got lots of stuff/bubbles in the water, or might there have been some current on the 3rd one ? On the 4th pic there are lots of electrical noise (that stripes going to the ground), and quite some stuff in the water coloumn, but wouldnt say any baitballs. From time to time you'll see lots of such reflections but you'll get used to it and it's actually pretty easy to spot the "real fish". Btw on the 2D Sonar you got some nice fish.
I've attached an pic where you can see noise on the surface from waves or whatever, noise in the water, and a baitball. It's a pretty large baitball in deeper water but i didnt find any good pic that fast. Actually i can just say that you'll know that its fish when you see it.
Greetings,
Del
//Edit: btw my attachment shows meters