Is environmental/marine science worth it? (details below)

Hello everyone! I am a 25 yo immigrant in Australia right now, and after a long and disapointing course in social media marketing which I found out not to be for me, I have decided to switch the trajectory of my life entirely. When I think about what I want to do with my life, I think about being in contact with nature, mostly in isolated places. I often times imagine myself in the middle of the ocean far away from any land, or in forests doing work there. In short, the more isolated and far from cities the work is, the more it seems to attract me. Moving from place to place wouldn't bother me too much since I've been doing that for a good chunk of my twenties anyways (and I love travelling!).

However, a quick reality check might be necessary, because I understand that no matter the career I try to pursue, you can't just work doing what you like all the time. From what I've searched online, not all environmental science jobs involve field work, and in the ones that do you don't do it all the time. Despite that, the field of environmetal/marine science attracts me a lot. My main worry is studying for it, because I've been away from any school subject for a long time, and I wasn't the best student in my school days either.

My favorite subjects in school were biology and geography, but that is not to say that I was good in them. Truth is, I was a terrible student, but not because I was dumb, I just didn't want to study at all. I never developed the habit of studying in my life, and my grades in high school were terrible because of that. Math, physics and chemestry were a nightmare, math being the one I liked most among those. But again, I just didn't like studying any of them, so I chose to play videogames instead. But now as an adult, I see myself wanting to pursue these careers but I'm scared that I wouldn't be able to keep up.

To top it all off there is the age problem. I understand most would say that 25 is still young, but if I take 5 years of my life just to study environmental science I would finish at 30 and be competing with fresh 24 year olds. Somehow thinking about that scares me, and I don't want to make the wrong decision at this point in my life, I just don't have the time to spare. I want to understand how the field of environmental/marine science is first before making the final decision. How is the market for it right now? Would an Australian degree allow me to travel to other places to work in the field? How difficult is it to sustain yourself with this career, and what paths can I take?

My plan is to study 1,5 years to get a diploma of conservation and ecosystem management, and then from there figure out if I really want to pursue this career. Moving to a bachelors in either environmental science or marine science which would take me 3 years to complete. I appreciate in advance for the replies, thank you!