File:Special Duration Up Chart.png

Formulas
x = 10*MainSlots+3*SubSlots

Bomb Rush & Inkzooka: Duration = [base duration]*(1+(0.99*x-(0.09*x)^2)/50)

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

Base duration for all special weapons:
 * Inkstrike (setup) & Killer Wail (setup): 10s
 * Echolocator: 9s
 * Inkzooka: 6.5s
 * Bomb Rush & Kraken: 6s
 * Bubbler: 5s

Unchanging Duration:
 * Killer Wail (attack): 3s
 * Inkstrike (attack): 1.5s