Tail 6-8 long saddle hackles plus Flashabou (1 set)
Skirt Marabou or schlappen wound at tail base (1-2)
Collar and head Spun/stacked deer belly hair, trimmed diver-style (6-8 clumps)
Weed guard (optional) Heavy mono loop (1)
How to tie it
Tie in a tail of 6-8 long saddle hackles, splayed in pairs, twice the shank length, with plenty of Flashabou over the top.
Wind a marabou or schlappen skirt at the tail base to blend the transition.
Spin large clumps of deer belly hair up the entire remaining shank, packing hard after each clump. A big diver needs dense hair to push water.
Whip finish and trim to the Dahlberg diver shape: flat face and low-shaved bottom, rising to a wide raised collar at the rear of the head; the collar acts as a diving plane that pulls the fly under with a gurgle on each strip.
Vary the hair density to tune it: more hair floats higher and dives shallow, sparser hair dives deeper.
Add a mono weed guard for fishing the slop, and cement the trimmed face lightly.