Worse. Way worse under saltwater.
Skin effect same as any other conductor. Travels great on and reflects off the surface great.
Discussion
What would be the best way to communicate over longish distances underwater?
Telepathy? Wires if there aren't sharks to bite them.
Hmm. I don't telepathy is reliable enough yet.
Very low frequency underwater acoustics. Still limited in range though (< 40 km.)
https://www.sercel.com/en/news/long-range-underwater-acoustic-communication-experiment