Back in April, Crowdstar promoted its Gamebar through Happy Aquarium, offering 10 free Pearls to those willing to install it. This time around, random players who start their game are getting a pop-up window advertising the Gamebar with the Rare Rainbow Shark.
Since not everyone is getting this notice, you should grab the Gamebar by clicking here to go directly to the official download page. Next, click on "Download Gamebar" for a 2.4MB file with the name: FFCrowdstarToolbarInstaller_CDS_tbr_1.9.0.0.exe
(NOTE: I recommend unchecking the box for "Make Ask my browser default search provider" because if you're after the shark, you really don't need it.)

Judging by the file name, you should be able to tell that this Gamebar is a newer edition than the one released in April, so maybe you'd want to keep it around to test it out.

After you've downloaded the Gamebar, double-click on it to run installation, then restart your browser. When you log back in, you should see the image below. Click on "Get My Shark!" and you'll get a baby Rare Rainbow Shark in your tank. And just like the first time around, the game should reward you with an additional 20 Coins for your trouble. Now, if you want to uninstall it, here's what you do:

If you're using Firefox, simply go to the top of your window for the "Tools" menu, scroll down to "Add-ons", look for the "Crowdstar Gamebar", then click "Uninstall". Firefox will restart itself, the Gamebar will be gone, and you'll get to keep the shark!

For Internet Explorer users, go to "Tools", scroll down to "Manage Add-ons", look for the "Crowdstar Gamebar" listed under "Ask.com", double-click on the name "Crowdstar Gamebar", then click on "Remove".