I bought an oooold Fishing Buddy at a yard sale, so old it's still made by Bottom Line and not Humming Bird. I like it actually good for finding structure, depth and when it meters fish I have started pulling them up sometimes. Especially crappie, bluegill and trout. Like Bayfishingjunkie said though the side finder is usless unless it meters a boat coming at you your about to get hit by.
Nice part is it's easy to use, easy to mount and uses regular batteries. I plan on upgrading mine after I sell a few bikes.
I've used mine on my tube, yak and retal boats all in fresh water. Havn't tried salt yet. I also have the small Humming Bird fish finder that you attatch to a rod and reel and then cast the trasnducer out. I tow it along on my float tube to look for structure, drop offs and depth... works ok for that but fish finding is a big maybe.