This was from my first time shooting in an aquarium. There were no people around the Pacific Sea Nettles, despite it being crowded most other areas. The jellies moved around randomly and the lighting in the tank was also changing. It was also very dark, so I decided to use a flash (ill-advised I now know). I got so lucky with: no crowd, the jelly staying still long enough for the photo, the light hitting it just right, and no flash reflection on the glass.