For many anglers the idea of float tubing with a fly rod brings forth visions of working a shoreline with a popping bug, or casting to the occasional rising fish with a dry fly. Indeed, that works very nicely if the fish are up near the surface. As with topwater bass fishing or dry flies, however, that amounts to only about 5% of your potential opportunities.
Fast-sinking fly lines allow you to cover the entire water column in less time.
Tapping into the other 95% of the catching requires looking into the advantages of sub-surface lines that get your fly down where most of the fish live most of the time. Very often, fly anglers will enjoy the sport for years before they even consider sink-tip or full sinking lines. However, plumbing the depths with streamers, dragonfly nymphs or bottom bouncers produces the vast majority of big fish caught by tubers.
By in large, this approach is dominated by 7 weight tackle and up. Trying to manage larger flies, larger fish, wind and sub-surface lines with a lighter outfit is like trying to pound a sixteen-penny nail with a hobby hammer. This is why the variety of different sinking lines offered by manufacturers expands significantly at the 7 weight level.
Sink rates are described in IPS, or inches per second. Whether you begin with a sink-tip or full-sink line, your most versatile first choice is one of the faster sink rate offerings. Starting here assures you can cover the entire water column in less time. If the fish are hanging nearer the surface, you simply begin your retrieve sooner and strip faster. Eventually you may fill in your arsenal with slower sinking lines for special situations, but a fast-sinking line is the best place to start.
Once the cast is made you begin counting the line down -- one thousand, two thousand, etc. Try different depths until you find fish, and then concentrate on that depth. If I'm fishing with a friend, one of us will work from the top down, while the other works from the bottom up until we zero in on the day's pattern.
If I'm prospecting a new trout lake, I'll focus around feeder streams. If I'm bass fishing, I'll begin around boat ramps, sharp drop offs, or other obvious breaks in the shoreline. If there is so much timber or vegetation that you're overwhelmed, pretend it isn't there, and focus on bottom contour.
Slack is your enemy, so put your rod tip under water, point at your fly, and keep the fly coming. When you feel a grab, do not lift your rod. This is a tough habit to break. Strip faster until you feel meat (strip set), and then lift. If the fish missed, you are in position to resume your retrieve.
One last hint: Don't use wimpy tippet, or you'll get your heart broken. One of the most exhilarating things about this type of approach is getting slammed in mid strip.
View all sink-tip and full sinking lines.