Give me a little while, and I'll find it for you. I've got "Windows 98 Plus!" on an old HDD somewhere.
EDIT: Okay, apparently it wasn't on my "Win98 Plus" HDD, for one reason or another, but it WAS on my WinME HDD.
Here it is.
It's an old Screensaver, meant for Windows 9x, so it took a little researching to find out how to make it work with XP. I found a little post somewhere that says how. I included the files needed.
Basically, extract the contents of that Zip file to C:\Windows\System32. Then, right click on the "Underwater.SCR" and click "install."
And there you go.