Sherman's aquarium is a xscreensaver hack, an wm(window maker) applet and a a gnome-applet too that shows a couple of nice animated fish that swim around. It can also display the current CPU load and the status of capslock,numlock and scrollock.
Does not compile properly on Linux Mint 17.2 with Cinnamon as desktop. Configure works, but make produces errors. Hopefully this can be fixed, since I love this screensaver a lot. I am glad to help with any information.