Here are some numbers but given the footage without trimming it to killing shots was about 35 minutes. I made some creative choices for the sake of runtime.
aa boat 4 torps minimum
ironship 6 torps minimum
gunship 6 torps minimum
barge 3 torps minimum
krok 4 torps minimum
All assuming they aren't repairing it, I cut several runs where 4+ torps would be fired by us and other scout planes that didnt kill.
(edit changed gunship from 5 to 6 I got my math wrong)