I don't like the word evolve but rather adapt.
Yes I think adaptation takes place instantly. Dolphins would of gone from land to sea in say five years after the flood.
The evidence that creatures change from one state to another is excellent. Only the mechanism and time is a problem.
I believe that marsupials are just the same creatures as elsewhere on the planet. So important, if minor, change can take place quickly. As long as a creature stays within its kind. Whatever that is.
The verse in the bible is correctly interpretated as giants of the deep and not whales.