Do you think they lay another cable from the tap to some collection point or do they use radio waves? Or maybe they just record the data and then just collect it by a surface ship or a sub every month...

They do a splitter in datacenters to the NSA so I presume that is similar many fiber optic wires. From what I understand is that the submarine has to stay there to collect the data. So I presume they split it and have a cable they connect to it that routes it right to the sub. However I think Hawaii is a big NSA station because a lot of those international lines right through near there. I wonder if they could split the stream and run a whole cable back to Hawaii with it.

https://en.wikipedia.org/wiki/Room_641A

https://www.washingtonpost.com/business/economy/the-nsa-slid...

https://wikileaks.org/spyfiles/files/0/55_201110-ISS-IAD-T1-...

Radios don't work so well underwater. This is why subs have various radio masts that poke above the surface. They stay just below the water with the antennas dry for the most part.

It's be much easier to mess with routing (in secret or not) and capture data at another point.