Understanding Fly Lines

Line Floatability

On the package of every fly line is a code. The third element defines the lines floatability. This tells the angler if the line floats or sinks. If it is a sinking line this further describes how much of the line sinks and the speed at which it sinks. Below is a discussion of the 4 main floatability indicators you will come across.

Floating (F) lines are made of materials that have a specific gravity less than that of water and are made to present flies at, or near the surface of the water. These lines have inclusions embeded in them that reduce their specific gravity to less than that of water, making them bouyant.

Intermediate (I) sinking line. This line sinks, but at a very slow rate of 1 or 2 inches per second. They are usually clear and are used to fish just below the surface of the water.

Sinking (S) lines are heavier than water and sink at different rates depending on their diameter (click for discussion of sink rates). These lines are used to fish deeper areas of rivers, lakes and oceans. These lines are usually labeled with a "Type" number which indicates its sink rate in inches per second. For instance a "Type IV" would sink at about 4 inches per second.

Sinking Tip (ST) lines are floating lines that have a length of sinking line integrated into the front end of the line. These tips can be up to about 30 feet in length depending on the intended usage of the line. Many of the moret popular salt water lines these days go a step farther and integrate a fast sink shooting head with an intermediate running line.