Yes-they came about because the BBC only played about two hours of pop music a week.And Caroline survived at sea on a variety of ships into the nineties.
It took making supplying them illegal to close most stations as broadcasting from international waters was legal.
There was a short lived one off the States I think(need to check that).
The Ross Revenge is now anchored in the River Blackwell.
In normal times there are trips to the ship(I hope to do one) and Caroline broadcast from her one weekend a month.
A friend on another forum can see her out of her window!
Now fully licensed -which was their aim from the start-Caroline are on medium wave ,DAB and online with four stations.And there are dedicated North American streams on their app,
And it is great to be able a listen to a station that is not Top 40 driven.