I am no expert on sonars or underwater cameras, but did recently buy a very inexpensive Aquavu type camera off of Tik Tok (The constant adds incited me over the winter). The camera only cost about $30 and I was expecting a total piece of junk. I took it out crappie fishing a month ago on my kayak to give it a try. This BOW is muddy, visibility of 1- 2 feet, and my hopes were not high. Once I found a school of them, I dropped the camera below and was beyond impressed to see multiple of them in and out of some lily pad sprouts. Camera was quite clear and was easy to ID the fish, indicate structure, and determine the substrate. I have not used it in any clear water yet, but with positive murky water results I'm sure it only preforms better in clear waters.
The downfalls I have found so far is the need to keep the unit charged. After running this unit for 2 1/2 hours the battery level had not dropped, but it is something to keep in mind (Bring a portable charger with you). The only other down fall I have found is its buoyancy. In my opinion it takes far too long to sink, but that was easily fixed with a 1 oz trolling sinker I had on hand.
It also has IR lights for low light situations, but I have not run into low enough light levels yet to test.
For around $30 it was a steal to ID what I'm seeing on my fish finder and see how the fish are interacting with my jigs/bait. I unfortunately do not have any pictures of the video quality and do not know the longevity of it yet as I have only had it out a hand full of times this year. The next time take it out I will try to remember to snap a few shots.