[Rick]

The Lyle gun was employed from shore by the Livesaving Service here in the US. I'm unaware of them being used on board a vessel; I suppose it could be used that way.
The most difficult part of employing the device was the proper faking down of the messenger line. If this was not done properly the shot would fall short and the line would have to be faked down again properly, which is time consuming.
Pictured a Lyle gun display and a picture of the faking board.