Deep Fishing allows you to find active fish, the sinking fly line will present your flies and streamers at the right depth. Sinking fly lines are essential for fishing in stillwaters. The sinking rate marking allows you to know and adapt the depth. Sinking lines are identified by the sink rate, for example S3 means that the line will sink 3 inches in 1 second or (2.54x3) about 7.50 cm second. You can set the depth for 10, 25 or 60 seconds and find the area where the fish will be most active.