Here’s a few shots from my Lowrance that I am having trouble understanding. I cannot tell if my colorline is off, sensitivity is off or what. Seems like it should be a little more obvious as to what I am looking at ? For example, Photo 1 looks like some type of structure. Are all of the black spots & squiggles interference ?
Here’s another picture. I am guessing there is something hard on the bottom on the left. Perhaps a rock. The blue lateral line on the bottom might be a log ? I threw some deep cranks down on it last year & was hoping to feel something. No snags hangups hits or anything. 
Another one that makes me go hmmmmmm. Looks like something standing upright & vertical in the water ??
and finally, is this suspended lateral line a fish ?
From my experience you’re not always going to be able to figure out what something is from 2D depthfinders, you’ll need to couple that with side imaging or camera work or something else like running a crankbait through something like you tried already.
I’ve seen things similar to your pic number 1 & 3 ending up being just a strand of weed. I remember once on a clean, sandy hump seeing a single, vertical strand of weed showing up like pic 1 & 3.
Pic 2 could be anything from a suspended weed to a small fish.
Your rock guess on pic 2 is probably correct and pic 4 looks like two fish to me but I have seen wood look like that as well.
The “interference” type stuff always boggles my mind but I do know that bubbles, insects and floating debris can all produce this. Probably not bubbles since those look more symetrical.
I think your sensitivity might be a little high.
It’s tough to interpret your screen without knowing how fast you are going (SOG), but the last pic is probably two or three fish moving slowly under the boat.
I’d suggest Understanding Sonar and Interpreting the Display I and II by Doc Samson. They are very helpful in trying to figure out what’s going on beneath the boat.
Check out this link too http://www.hightechfishing.com/pdf/charttutorial.pdf
Pic 1 was approximately 5 mph. 56 degree water temps in October 08. High algae content lake & very murky water clarity. All pics are the same lake.
Pic 2 = 0 MPH (drift)
Pic 3 = 4.74 MPH
Pic 4 = 0 MPH (drift)
When I adjusted the colorline to the lake, I tried to adjust it to the level of silt in this lake. That puts me at approximately 72%. Sensitivity was at or over 86%.. Possibly 92% but not sure.
Thanks for the help & suggestions so far.
From Doc Samsons videos pics 1 & 2 could be thermocline
I will take some guesses as many things look the same on sonar.
Photo 1
1. Black spots are something small
Photo 2
1. Yellow bump could be a rock
2. The last ½ appears that you slowed down and the lines on the bottom are some type of structure either man made and the thick blue line connecting the bottom bumps could be a fish.
Photo 3
1. The yellow fat arches are nice fish
2. The vertical “post” I don’t know, it could be the display combining multiple echoes.
Photo 4
1. The 2 horizontal yellow lines are fish
I am leaving for the Red Wing FLW tournament today so don’t ask any more questions from me, please.
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