MSB Questions

Why and/or how does water get contaminated/polluted? How long does it last and how can it be reversed/fixed?
We all know that the seas are contaminated, but I want to know how exactly they became that way, and how many ways a body of water can become polluted. And we also know that sewage spills and such can be cleaned up, but how does that work? I want to know who cleans it up and how long it takes. Maybe I'll interview someone who does this to find my answers.

What type of sicknesses/illnesses can humans/animals get from the water? Is it dangerous/life threatening?
There was an article from last year's MSB that I read that told the story of a man who got sick from being in the ocean instead of getting better, like how he used to. I want to know what sicknesses he got, and what other diseases might be out there. I can talk to that man, a doctor or expert on these kinds of diseases, and maybe a vet or marine biologist. I want to know if animals can get sick too.

Can life like fish thrive in environments contaminated by sewage or high bacteria levels? Can coastal pollution affect the behavior and/or evolution of marine life or other animals?
When we went to the bay, I saw fish and snails in the water, and I wondered--if the water was polluted, how could they thrive? I know the bay isn't disgustingly dirty, but in some other place, can life thrive? Can plants grow green or fish grow big, or are their evolutions affected by the pollution so that only the fish that can last through the pollution live? Bacteria might affect their growth too. Maybe I can find a marine biologist to talk to about this.