3D Desktop Aquarium is an aquarium simulator that can be run as a dynamic wallpaper and/or screensaver.
Even though the graphics are pixellated and there is a prominent button and placeholder image that advertise the developer's other "useless" offerings, the smooth animation of both dynamic fluid and fish movement, as well as the diversity of fish available in the full version compensate for those shortcomings in my opinion. The aquarium is highly customizable as a bonus, with up to forty fish on the screen at a time in a variety of sizes.
Sam's Protip: It appears that version 1.9 broke several features of the application, such as use of certain backgrounds and distortion of water based on the Mac's motion sensor - cool if they worked right? But not quite as cool as sharks, which version 1.9 added, so I think it's a fair trade.
Pros
- Nifty synthesis of screensaver and dynamic wallpaper
- Aquarium full of sharks = win
Cons
- Pixellated even on smallish non-Retina monitors
- Application must be open and present in the Dock to function
- Some desktop images not supported for translucency feature