@XxTheNarwhalQueenxX
I'd recommend a mix of your passions! You seem to like Teen Fiction and ocean animals, is there a way to merge that?
If you're stuck for ideas, I'd also start reading other peoples work and constantly ask yourself "How would I write this?". Eventually, it's gonna spark an idea and you're going to end up writing a story that you want to write.
If you're really stuck, I suggest starting small and just writing a short story or two as a warm up. I only have short stories completed from some of my writing classes.