Can you give me details on these careers?

I love games so I may want to be a game designer. But I'm also interested in animals. So I want to be a game designer, vet, or marine biologist. I'm twelve years old, so can you tell me what I can do to get a head start if you know what I mean. I got my Open Water Diver scuba certification when I was ten years old. So that may open up some doors. Can you also give me details on these careers like annual and weekly salary, traveling, what it's like, promotions, what they do. I know about some things but I want more info. Because some people think being a Marine Biologist is boring and doesn't give you many job opportunities. Can someone please tell me why for all jobs.