Colin P said:
Actually a fleet of small AUV's operating in the choke points would be better, they patrol those areas using passive and active means , pop to the surface and announce a suspicious contact. You can have local communities service the AUV's for the basic bits like fuel or batteries.
You detect, track and identify in advance of, though near, getting to the actual choke point. The actual choke point, where sea room is minimized and escape routes more limited is kept for the actual hunt and kill box.
Actually, I just re-read your post and ... double negative on that.
Simply, here's why. In the air, wether a MPA or a UAV, the idea is pinpoint locate then hunt to kill. The AUV's you propose are for early detection and general tracking. We already have that, from WWII and with improvements ever since: It's called SOSUS nets. And you don't have to have anything pop up and announce: there are human operators monitoring the actual system directly and in real-time.
And they happen to be located in small communities, like Shelburne, where they do help the economy with their "basic bits" purchases such as fuel, food and board. ;D