Evolution Hypocrisy?!?!?

Doing a little research into my science book I kept running across this "fact" that through "perfect" cirstances; through billions and billions of years. That we evolved from water into humans! Though this sounds crazy, or logical...I am wondering how does this not violate the 2nd law of thermodynamics? (Things naturally have the tendency to decay; i.e. leave metal outside i rusts) If we were to be "evolving" up (maturing) then why do these same mutations that made us who we are today hinder us? Thus revolving back to the 2nd law of thermodynamics, if humans are digressing because of mutations (i.e. Autism, cancer, and other mental disorders) Why do scientist proclaim that mutations made us smarter and not dumber? I do believe in Micro-evolution (more or less adaptation), best example is with Darwin's finch's you put an animal into a new environment he will change physically to be able to survive; but none the less in Darwin's finch example the end result was a finch. How does a new beak prove that a Finch will turn into a shark because you shove it under water? Wouldn't it just drown? Simply my question is how can Macro-evolution exist by saying animals adapt and the 2nd law of thermodynamics exists?