A helo has to operate from some platform. Sink the home of the helo, and your air coverage is reduced
Everything has weaknesses. It's a military job to exploit, or defend those holes. A sub that gets a fish into a CVN may well pay, but maybe being a glorious martyr is an adequate trade. These are people that rape little boys for fun. They don't think like humans.
I was thinking if the helo deployed ACTIVE sonar before the sub attacked -- granted, with the volume of ocean to cover, it's a long shot. But the heli is impervious to attack.
Cheers!