Samira ADC vs Nautilus Support Matchup
Samira ADC wins 52.8% of 3,680 Low Elo games against Nautilus Support, +1.9 points vs expected, 2-patch window 26.19-26.20.
Researched on LoL patch 26.20. Tips are written to hold at any rank; stats come from Low Elo ranked games up to patch 26.20.
Why Samira is favored
Samira's Blade Whirl(W) can destroy Nautilus's Dredge Line(Q) projectile, so she can deny his main skillshot engage when she holds it for the hook. It does not stop Depth Charge(R), which means Samira still has to respect his targeted ultimate and wait for his crowd control before committing to her own R.
How to play as Samira
Hold Blade Whirl(W) for Nautilus's hook; if he targets you with Depth Charge(R), W will not stop it, so stay back and wait out his crowd control before using Inferno Trigger(R).
If Nautilus catches you with Q and follows with his passive auto, Cleanse after the auto connects so you do not waste it on the hook alone.
Blade Whirl(W) can destroy Nautilus's Dredge Line(Q) projectile, but it does not block his Depth Charge(R).
How to play as Nautilus
Do not throw Dredge Line(Q) into Samira's ready W; wait for her to spend Blade Whirl, or use Depth Charge(R), which she cannot intercept with it.
Nautilus's ultimate is not a missile that Samira can destroy with Blade Whirl(W), so it remains an engage option after she blocks his hook.
Sources
These notes come from r/SamiraMains, checked against the champions' abilities.