I am not too interested in the Public Health Service, but the second link, NOAA seems to be something I might have an interest for due to it implementing most of my interests into one. I think because I will finish in the fall of this year I could possibly sign up for it, but I want to weigh the options first. I wouldn't want to be behind a desk but out in the field first. To answer your question though, I believe infantry would be a good start. Does the NOAA provide any sort of field component to the marines portion?