The Canal & River Trust have a useful PDF Boater’s handbook available for download, free of charge, from this page; there is also a video thingie.
The handbook naturally concentrates on British inland waterways, with narrowboats on canals and rivers but not on lakes, but there is nonetheless much useful material. Even experienced boaters might find it of interest, if only for briefing any non-boaty friends they’ve invited along for a trip.
Irish waterways history 