File:Special Duration Up Chart.png

Formula
Bomb Rush, Bubbler, Inkzooka, Kraken: Duration (s) $$= [base duration] * (1 + (0.99 * A - (0.09 * A)^2 ) / 50)$$

Echolocator, Inkstrike, Killer Wail: Duration (s) $$= [base duration] * (1 + (0.99 * A - (0.09 * A)^2 ) / 75)$$

Note: Attack time for Inkstrike and Killer Wail does not change with Special Duration Up.