A recent comment from Soulgirl: 'What is sculling?' prompted me to find some images which clearly show the difference between sweep rowing (the sort of rowing that I do and James coxes most of the time) and sculling.
The crucial difference is that in a sweep rowing boat, everyone holds one oar, known as a 'blade' each, and in a scull, each rower has two oars, known as 'sculls'. Sweep rowing is more common on the Cam, mainly I think because it has so many corners that lots of practice and skill is required to be able to steer and row well on this river without a cox - the smaller sculling boats don't have coxes, except for some training quads. Sculling is a much more symmetrical movement, and juniors are not allowed to begin sweep rowing until they are fully developed.
These images, from visualdictionaryonline are the best I've found:
Sculling boats. Quads, quintets and octuples also exist although the latter two are rare!
Sweep rowing boats
4 hours ago