I am getting ready to buy a Deeper fish finder. I used one once before and they are really cool. It is basically a transducer that you can cast and then it connects to your smart phone via Bluetooth. You can cast it or attach it to a kayak or canoe. As you reel it in or drift along you get live sonar, water temperature, depth, etc. It is a game changer for fishing from the bank. There are plenty of demonstration videos on YouTube.
https://buydeeper.com