Bad analogy. I would say that just because I can walk to my kitchen does not mean that I can walk to Australia.
Microevolution helps determine if my children will have red hair. But determining that a land animal can walk into the sea and, over time, evolve into a whale is to see genetic change on a very different level. I believe you see it as "the same thing, only more of it" and I see that as a substantial logical leap. I don't believe we have proof that you can get there from here.
Evolution is not something to believe in, it is a matter of accepting the available evidence
If you take micro-evolution has we have observed and give it 4.5 billion years you will end up with the diversity of life we see today.
Lets take a look at the wolf, if man can turn a wolf into a Chihuahua in a few hundred years, just imagine what nature can do given billions of years.
You are presenting an Argument from personal incredulity. Just because it is something that we cannot understand is not proof that God did it.