The delivery rose sharply and caught the Australian batsman just below his helmet and - although a painful experience for Watson - was a fine example of an accurately aimed short ball.
Nottinghamshire quick Broad has also targeted Michael Clarke throughout the series - with considerable success - and gave the Australia captain plenty of short deliveries to deal with during his short stay at the crease on Wednesday.
So how, as a batsman, do you deal with bouncers from the likes of Broad?
Nasser Hussain, Michael Atherton and Andrew Strauss joined Ian Ward in the Ashes Zone to demonstrate how they coped with the short stuff during their careers.
They explained ducks, sways and riding the ball; how you can look to score off short deliveries; and also considered effective field settings for a batsman struggling against the steeplers.
Check out the video above to see their masterclass - which ended in rather undignified fashion for Nass when Strauss' superbly aimed serve proved too good for the former Essex ace!