Could that possibly imply a biblical style flood?
Nah, that's all fantasy. </sarcasm>
Why are kangaroos native to Australia, and not anywhere else?
G-d must have created them, and then put them there, which is both special creation and special delivery.
Darwin's experiments on the transmission of various forms of life by various means were extensive, though of course, not exhaustive.
Since many forms of life are common between Europe and Britain, one would expect that the sea barriers between them was recent.
A simple look at the sea floor shows great furrowing in the channel, especially in the narrows.