Dive is a weak verb that recently people have been treating like a strong one

AHD4 has some interesting things to say about dive, pointing out that it is a conflation of two OE verbs, dyfan and dufan: http://www.bartleby.com/61/11/D0301100.html

They fail to mention, however, that, while dyfan was weak, dufan was strong. Its ablaut series was u, ea, u, o. Maybe, if I dig around long enough, I'll come up with a MnE verb that comes out of this ablaut series.