you are showing a lot of noise, you need to decrease sensitivity. if it is decreased then you are getting a lot of disturbance (boat wash/bubbles) with the ducer mounted it that particular spot, i would try lowering it to the 3 holes right below it. DSI needs a near perfect flat/level mount in order to read properly.
i suggest, if you have not already, read through the manual as it really does contain useful information on how to use the unit and tweak it properly; yet, it isn't all encompasing. to get a good DSI reading i suggest a minimum of 3mph boat speed. anything less and it won't really do so well unless it is on the slow troll setting.
also, try mounting a 1/2" thick piece of starboard to the transom so you can move the ducer around without putting a bunch of holes in the transom. it will make it less painful when you need to relocate it.
“For there is one God and one mediator between God and men, the man Christ Jesus, who gave himself as a ransom for all men—the testimony given in its proper time.”- 1 Timothy 2:5-6