Desktop Fun: Interactive Aquarium For Linux / Windows / OS X

Fsh is an entertaining interactive desktop aquarium. It was created as an alternative to Gnome easter egg called "Free the fish" for other operating systems.

Original gnome desktop easter egg

Type alt + f2
Type free the fish
Press [Enter] key.

To kill fish type alt + f2 and type command:

pkill gnome-panel

Say hello to Fsh

From the project home page:

Fsh was created because I wanted fish on my desktop. I have a coworker running Linux, and there's a feature (freethefish) that lets you have a fish swimming around on your desktop. I'm running Windows, so obviously, if I wanted a fish, I was going to have to do it myself.
Since then, fsh has added a number of features. You can have basic fsh, ninja fsh, invisible ninja fsh, sharks, laser sharks and barracuda. Sharks will eat anything except other sharks, while barracuda will eat basic and ninja fsh. Ninja fsh take the fight to the predators, and actively hunt down sharks and barracuda. Laser sharks will shoot at anything they can eat once it lines up with their laser.
You can customize how many of each fsh you get, along with a number of other parameters (like whether predators eat or just kill, whether to show blood on kills, etc) using the fshConfig program.

How do I install Fsh?

Type the following wget command to grab fsh:
$ wget http://nchc.dl.sourceforge.net/project/fsh/fsh.jar
Sample outputs:

 
--2012-09-09 10:54:31--  http://nchc.dl.sourceforge.net/project/fsh/fsh.jar
Resolving nchc.dl.sourceforge.net... 211.79.60.17, 2001:e10:ffff:1f02::17
Connecting to nchc.dl.sourceforge.net|211.79.60.17|:80... connected.
HTTP request sent, awaiting response... 200 OK
Length: 122216 (119K) [application/java-archive]
Saving to: `fsh.jar'
 
100%[==========================================================>] 1,22,216     176K/s   in 0.7s
 
2012-09-09 10:54:32 (176 KB/s) - `fsh.jar' saved [122216/122216]