I guess "exploded" refers to the fact the fuselage was intact i.e. a pressure vessel. When it hits the water hard, the lower surface is first distorted up / inwards, markedly reducing the "volume" of the pressure vessel. Hence pressure rises beyond the structural limit and in itself causes failures.
Given the nature of impact, I suspect it also gets into complex fluid dynamics with shockwaves etc.
All fairly academic I would think?