Before a recent trip to Chile and Argentina, a friend who runs a lodge down there said “Don’t forget to bring a sinking line around 200 grains.” Naively, I made some comment like “I’ll just bring a floater, that’s why God invented tungsten cones” but at the last minute I packed a 250-grain Depth Charge line. And I learned a lesson—never go trout fishing in big deep rivers without one. I always take a Depth Charge when saltwater fly fishing but never on trout trips.

Time and again on this trip, when fish were deep in lakes or in big oxbows known as lagunas down there, it was either fish a Depth Charge or go fishless. One day, fishing one of these lagunas, I was really banging the fish and my friend Peter was not. He was fishing a Streamer Stripper line. When I offered to switch rigs with him, he immediately began catching big brown trout and I drew blanks.

The Depth Chargeis a versatile line. Its density drives a line through high winds. Retrieve quickly and your streamer runs just under the surface. Mend and let it sink and you can fish 12-foot pools in fast water. And don’t worry so much about matching line sizes to rods. We give line size designations to these lines, but it’s really the sink rate that counts. I find I can cast a 200-grain line with a 5, 6, 7, or even 8-weight rod and either a 200- or 250-grain line seems to handle even the fastest, deepest trout streams. (For saltwater, I fish a 500-grain line, which is supposedly for a 12- or 13-weight rod, on anything from a 9-weight up.)

For saltwater, you gotta have a Depth Charge if you fish anything but shallow flats. And for trout fishing, I know I’ll never leave home without a 200-grain version for trout fishing.

Without a Depth Charge Line, Author/naturalist Peter Matthiessen would not have been able to get his streamer down to this fish.