~2 in/sec, the lough workhorse. A 10-count is about half a metre.
Fly lines
The sinking spectrum: floater to Di-7
Draft reference — pending review.
What it's for
Lough lines are a depth system. 'Di' numbers are sink rates in inches per second — Di-3 sinks three inches a second, Di-7 seven — and with a countdown they put your team at a chosen depth, cast after cast. The spectrum runs floater, midge tip, hover, slow and fast intermediate, then Di-3, Di-5, Di-7.
The beats
Floater
Stays on top. Dries, the washing line's backbone, the bung. Depth comes from the leader, not the line.
Midge tip & hover
A floating body with a short slow-sinking tip holds buzzers just under the film; a hover sinks the whole line at under an inch a second and hangs flies level in the top couple of feet.
Intermediates
Slow (~1 in/sec) is the classic top-of-the-wave wet-fly line. Fast (~2 in/sec) is the lough workhorse — count to ten and you're about half a metre down.
Di-3 / Di-5 / Di-7
Mid-water, deep, and get-down-now. A 20-count on a Di-3 is roughly 1.5 m; on a Di-5 about 2.5 m; a Di-7 reaches 4 m in around 22 seconds and hugs the bottom.
The countdown
Cast, count, retrieve. Same count, same depth, every cast — and when a take comes, the count tells you exactly where the fish are sitting.
Common faults
Not counting the line down
One cast fishes at two feet, the next at ten; a taking depth gets found and instantly lost again.
Fix: Count every cast down before the first pull, and change the count — not the retrieve — until the takes start. Depth found by accident can only be repeated on purpose.
When you'll use it
- Reading the Line block on your Tactical Card — this is what those names mean
- Fish holding at a known depth: pick the line whose countdown maths reach them fastest
- Early season and cold snaps, when everything happens near the bottom
Related
Sources & how we know this (3)
- Di ratings are sink rates in inches per second; floating to Di-7 spectrum and typical fishing bands
The Essential Fly — Fly line sink rates explained: floating vs DI3/DI5/DI7 · 2026-07-11 - Midge tip and hover behaviour near the surface; intermediate sink rates
Guide Flyfishing — RIO midge tips & intermediates · 2026-07-11 - Countdown method for repeatable depth with sinking lines
Guideline — Sink rates & depth control · 2026-07-11
Draft reference — pending review.