This is a very simple live wallpaper, made just for fun.
Press on the screen to change direction of movement.
To install: long press on the home screen and select Wallpapers->Live Wallpapers (or through the menu). There is also a button in the app that does the same thing.
Now available as a Daydream also (for devices with Android 4.2 and newer): https://play.google.com/store/apps/details?id=gr.jvlach.sillyfishdaydream
Graphics by OpenClipart (https://openclipart.org/)