According to NOAA, the average depth of the ocean is 2.3 miles, which is a little over 12,100 feet. Even if we take into account that the majority of the fish that we want to catch live in the upper 200 meters of that, we are still talking about depths of over 650 feet. Suddenly those heavily weighted nymph rigs look pretty tame, right?
It’s obvious that when we need to get down to fish that are feeding in deeper water that we need something more specialized than the generic floating line. Fortunately there are a wide range of fly lines that are designed to get down in the water column, dragging a fly into the depths. Most modern sinking lines are divided into three categories: intermediate lines, sinking lines, and hybrid combinations of floating lines with a short length of intermediate or sinking line attached at the front. These so-called ‘sink tips’ offer anglers flexibility of being able to get their fly deeper into the water column with the easier line handling of the floating running line.
Pros of sinking lines:
High density and low diameter makes them easier to cast and fish in wind, heavy current and rough surf conditions.
Wide variety of sink rates, usually measured in inches per second (IPS)
Enables the use of short, stout, untapered leaders
Allows reliable access to the top 100 feet of the water column.
Can cast very large, bulky flies that would be otherwise difficult to manage
Can be difficult to cast
Line management is difficult, being more tangle-prone than floating lines.
Sinks quite slowly compared to comparable conventional tackle.
Typically best used with a stripping basket of some kind
The earliest fly lines were also sinking lines, using natural materials like hair or silk that soaked up water and sank slowly, which advanced to lead cores and finally the modern version using powdered tungsten mixed carefully into the coating to provide predictable sink rates.
But enough with the history lesson. Let’s discuss situations where a sinking line or sink tip could be the best choice, how should you go about casting that sucker?
As we discussed in the last article about casting different weights of flies and what the impacts on our casting might be, it can be useful to think about how a fly line interacts with the weight of the fly. Sinking lines are of course more dense than floating lines, and this can be used to our benefit to move bulkier flies with less effort. The obvious drawback is that sinking lines feel quite heavy, which can result in exacerbating a variety of common casting faults and really make for miserable casting.
When I am teaching students how to begin casting a sink tip or full sink line, I will usually have them start with short casts to get a feel more the increased density and perceived weight of the line. Picking up the initial backcast can feel a bit more awkward than usual, since the line typically ends up below the surface of the water. Our first job is to find a way to get the line either to the surface or nearly so - this can be accomplished with a roll cast or by waggling the rod tip while lifting the rod into casting position. A drawn out haul can help accomplish this as well, and if the rod has a fighting butt I will often brace that against my forearm as I lift into the backcast for extra leverage. Now for the trickier part - maintaining the speed of the line without hitting the rod or yourself.
There is a style of casting known as ‘Belgian casting’ or ‘oval casting’, both of which reference the use of a more circular style of backcast where the rodtip travels out-and-around-and-up behind the caster on their strong side. This would normally be considered a casting fault if we were discussing more typical casting strokes, but due to the heftier nature of sinking lines we can turn a fault into a desirable outcome.
Belgian casts allow two main things to happen, the first of which being we keep the line and fly well away from ourselves. If you’ve ever tried casting sinking lines, you’ll know this is a key aspect to not getting inadvertently perforated or hitting your rod. The second, slightly less important aspect is that the lack of the typical ‘form a loop, come to a hard stop, reverse the direction of the rod, hard stop’ casting form that we think of for most fly casting applications. Instead the outward and upward curve of the Belgian cast sort of smears things together into a more cohesive unit that protects the entire system from loading up too much and possibly breaking down. That is not to say that you can’t cast great loops with a sinking line - you can. But the Belgian has a hidden advantage, which is that it can be less tiring to use than a typical fly cast. This is a nice perk, since most of the time when we are throwing sinking lines we are blind casting and trying to cover as much water as possible as opposed to only casting when a fish is sighted.
The last couple things to talk about have to do with speed. When casting these heavy lines, I find it’s helpful to start slowly and deliberately before building up speed to deliver the fly. Try to work with short sections of line at first; if you’re throwing a sink tip, strip in until the sink portion of the line is inside the rod guides before attempting to cast. Get the fly moving and nearly to the surface before the pickup as well. Be careful about overpowering the casts - these heavy lines need more control than applied power. To that end, more advanced casters will find it useful to slip a bit of line to cushion the presentation cast to keep it from slapping the water.
A few bullet points to round out the discussion:
Slow tempo down, build momentum slowly and then stay out of the way.
Lean the rod tip well off of vertical to the casting hand side.
Get the sink portion in the guides before trying to cast.
Roll cast or otherwise lift the majority of the line to the surface prior to casting.
Cushion the back and forward loops with slight line slips, and cushion the presentation cast similarly.
Beware of overpowering presentation cast, will kick hard away from rod hand every time.
Minimize false casts whenever possible.
You’ll typically choose a short, stout leader.
Good for cutting through wind and surf.
Difficult to manage, sinks and tangles even more than floating lines. Recommend a good stripping basket.