This is my first time (properly) implementing opacity maps. I used Maya for modeling and substance painter for my textures. I created alpha brushes for the leaves and flowers out of royalty free images. For the kelp, I drew the alphas myself, as there are not many kelp pictures free to use.
I am pretty happy with them, for the most part. However, I think my tree is a bit cartoonish. I think that I can improve in terms of realism as I get better at modeling. The kelp and the lilypads look pretty realistic, as far as a beginner's models go, though you have to look at the kelp up close to see the different patterns.