To mark your braid to the depth sounder pick a calm day, stop your boat where your sounder says its 20m and tie a simple loop in your braid line. Pass a short length of trace nylon through this loop and tie a simple knot. Trim the nylon back to about 2mm on each side of the knot. Repeat for 25m and 30m. Leave the nylon slightly longer for each depth.
When you see a fish on the sounder you simply lower the line to the depth the sounder says,(say 23m)and you will feel the first knot hit your thumb as you lower it (20m) keep lowering till you hit the second knot and stop the reel. Your sinker is now at 25m. wind up slowly till the fish hits your fly. If you get back to the first knot, lower it again and repeat. most fish strike a slow rising smelt. Most feeding fish are between 20 and 30 m deep on lake Rotoiti!