Enjoy the mysteries of the sea from the safety of your own terminal!
Russel Goring has updated J. Sommer's Windows screensaver, and has posted the source code on Github.
If you're running Mac OS X, Chuck Houpt has put together a packaged version that will run out of the box.
Michael Pyne and Maksim Orlovich wrote a KDE Screensaver based on the Asciiquarium. At one time it was included as part of the kdeartwork set of screensavers, but apparently KDE doesn't like screensavers anymore.
Claudio Matsuoka created a live wallpaper for Android, but it doesn't seem to be available anymore.