Follow my heart or be practical?

So I’m 21 I haven’t started college yet for a few reasons but I’m finally ready to go.The thing is I don’t know what to go for. My heart has always wanted to go with marine biology, I’m passionate about the ocean and conservation and would love to have a career helping the earth, but I know it’s extremely hard to make a name for yourself and a good living in that field, so part of me says I should go to school to be a nurse, i don’t think I’d hate it, it’s consistent and there will almost always be a job for me. I don’t want to wait on school any longer and I’m planning on starting this summer but I’m so conflicted on which direction to take and I’m running out of time!

If anyone has any advice that would be much appreciated!!