Well, you can do 3.5 Mbps ADSL over wet string[0], which is about 5 channels of uncompressed 16-bit PCM at 44.1 KHz.

[0]: https://www.revk.uk/2017/12/its-official-adsl-works-over-wet...

Using acoustic data transmission because it is easy and I am lazy, I'd guess comparable to copper wire broadband based on the short distances involved in an average tin-can + string operation.