Carp fishermen use this and I figure I would pass it on. Eich, feel free to correct or add anything (he's a carper). This is a really simple way to get a somewhat accurate measurement of depth in a lake or pond. It works well in still water, not sure about current. 1. Mark out one foot on your rod starting at the level wind or the bail on a spinning reel. 2. Start out with a simple Carolina rig with a heavy weight (at least 6 ounces.) 3. Instead of a hook, rig a round plastic bobber on the end of your line. 4. Cast your line out just beyond (a few feet) the area you want to measure. 5. Reel in the slack in your line in until you start to drag the weight along the bottom. The bobber should be on the bottom right up against your swivel. 6. Keeping your line TIGHT, release the spool or loosen the drag and start pulling line out in one foot increments. 7. Keep count of how many feet you've pulled out until you see your bobber break the surface. Good luck!