Thank you for stepping by! You are absolutely right about the fish photo. I just used a polarizing filter which allowed me to totally cancel the light reflection on the water surface. And the camera is just a regular Nikon D3300 with its default lens (18-55mm), so it's possible to take great pictures with non-professional gear too.
What I also did with all the pictures is adjusting the levels to make them look a little brighter than the original.