One of the most important things to master when you are nymphing from a drift boat is to be able to cast your rigg to the correct seam and them manage the indicator and flies to dead drift correctly.
Mending
1. When side drifting from a drift boat under indicator the idea is to set up a drag free drift.
2. Once the indicator lands, Stack mend the tip of your fly line directly behind the indicator.
3. It is best to try to have about 2 ft. of fly line above the indicator which will help slow down the drift of the indicator.
4. The water at the surface always flows faster than the water where the flies are drifting.
Control During the Drift
1. Point your rod tip at the indicator and mend almost constantly to keep the line fairly straight to the indicator.
2. You can actually mend and place small wiggles in the line between the rod tip and the indicator.
3. If your line is flowing faster than the indicator make small upstream mends without moving the indicator.
4. If the line is flowing slower than the indicator make small downstream mends without moving the indicator.
5. If the whole rigg is just not floating right, start over and reset with another backcast, a water load forward delivery and you’re right back at it.
Summary
Learning good line manipulation techniques will have your line throbbing more often.