The ocean is so big that some people call it "the last great frontier." There is so much of the ocean we have not explored.

SeaQuest DSV

I really enjoyed it on Netflix, although it never found it's voice.

yet I read that every meter of ocean floor was physically 'plowed' multiple times over by fishers, on average.

Where did you read that? It can't possibly be right: the Pacific alone is 160M km^2.

Maybe they mean the area of ocean floor plowed > area of ocean, but the same parts of the ocean are being plowed over and over again by fishers. Most of the ocean is not being used for fishing.

Not even close. Coastal regions, yes. But go out of costal regions or below a kilometer of depth and it gets awfully spotty.

Military networks have been substanially cut back in recent decades. The far north, and most all the southern oceans, are no longer a focus. No risk of russian subs, no listening.

Genuinely curious if you know: Has there been any effort to revisit this in recent years? I'm curious given the rise of China + Russia in the Arctic and China's demonstrated belligerence in the Indo-Pacific. [1,2]

1 - https://breakingdefense.com/2018/07/china-russia-in-the-arct... 2 - https://www.newsmax.com/philipguthrie/china-pacific-taiwan-u...

Large ballistic missile submarine fleets and a military posture that makes an attempted first strike likely are the main reasons to maintain such a net.

China has 7 active ballistic missile submarines. The US has 35 active nuclear attack submarines.

It's probably cheaper to run a less thorough net and then task subs to shadow any contacts made.

>> Large ballistic missile submarine fleets and a military posture that makes an attempted first strike likely

It was in the past. Today such things can be used for all sorts of intel tasks. Sosus is real time info about positions/speeds of all ships, surface or not. Satellites cannot do that. I imagine that the US is also using sound to monitor Chinese building activities in the south china sea. There is also, probably, some economic intel to be gained by monitoring shipping/fishing fleets, again, in a way not easily replicated from space.

Per Wikipedia, 68 active US subs. All are nuclear powered, 18 carry nuclear weapons.

Wikipedia apparently has different numbers on different articles.

You're only going to be shadowing ballistic missile submarines with attack subs, which means (total nuclear boats) - (18 Ohio class).

Based on the individual class pages (LA, Seawolf, Virginia) there are 53 active SSNs.