Complex sentence: Today only one lower Clyde shipyard survives, next to Newark Castle, Port Glasgow, at the point where the firth becomes the River Clyde, the site of the former Greenock shipyards are currently being regenerated.
Split into simpler sentences: Today only one lower Clyde shipyard survives, next to Newark Castle, Port Glasgow, at the point where the firth becomes the River Clyde. The site of the former Greenock shipyards are currently being regenerated.