I do search and recovery work so I'm mostly interested in locating structure to help divers / ROVs navigate in poor visibility. I finally broke down and bought a GPSmap 741 and PS-31 transducer. I temporarily mounted the transducer to the stern of my boat while tied up in the marina and pointed it towards the middle of the marina's channel. Here's a screenshot from today's test with some notes. So far I'm pretty darn impressed. The piling and floating dock in the distance are pretty easily identified. I saw a fairly large object swimming which I'm guessing was a skate.
I do wish Garmin made the depth scale and boat icon either much smaller or allow us to turn them off all together. They take up so much of the screen!
The bottom contours are really easy to read, but tall structure not always as easy. Any advice on how to more readily identify structure (posts, etc.)?