I'm thinking of joining the military but which branch?

I do OK in school but I have never liked the repetition of cles. Most of what they teach in school is purely for academia and not real world practical. My GPA at High school and Junior college was 2.5 on a 4.0 scale. I like working with my mind and hands! I'm an Eagle scout who was captain of our high school swim team. I have been a lifeguard for 4 years and the past year worked as a guide in Canada at an exclusive resort. I have always dreamed of having a career in the outdoors. Maybe with Fish and Wildlife or National Parks. I need to get a degree to do that and am thinking of joining Navy, maybe as a rescue swimmer. Also thought about Coast Guard, but I'm worried about my gpa not being high enough. Someone said join Navy and later transfer to Coast Guard. Is that realistic? If I enjoy the Navy I could see making it a career. Is it common to first enlist and later try to become an officer? As you can see I need some true and honest guidance.