I'd assume the quickest was is to drive to the Lake District from Oxford. You will have to get the M40 (north) towards Birmingham, Get on to the M42 and then on to M5 going north. When the M5 ends...
There are 14 main bodies of water in the lake district but only one official "lake" and that is Bassenthwaite Lake.
All the rest are "meres" or "waters", for example Windermere, and Coniston Water.