Concerning Tzphardea, Rabbi Hirsch 7 27 writes צפרדע can not mean crocodiles, otherwise there would have been no Egyptians left in the land. It is clear that they were only annoying creatures, not dangerous ones. Tradition has it that they were frogs.
How can he claim 'otherwise there would have been no Egyptians left in the land', they survived Arov, the mixed wild beasts? Is there any reason to assume they could survive Arov but not Tzphardea?