I have the EyeSea Mariner. It works pretty well. It will generally get me within 15' or so of the anchor line. Sometimes the display will hop around a bit, but once it stays steady in one direction, it is reliable. Also, you can double check by making sure the distance number is getting steadily smaller as you swim toward where it says the sender is. It gets confused if there is something large between you and the sender, like a piece of wreckage. I recently used it in San Diego and had no problem in kelp. I used it there near some rock cliffs (Coronado Is) and the readings weren't completely reliable until I got away from them a bit. Perhaps there were some echos. Overall I've had pretty good luck with it .
