The search box floats. Not as decoration, it actually bobs on the surface, and if you shove it with your cursor it takes a second to settle again.
Type the words. Something happens.
More fish please is the one everybody knows, and it works here exactly like it should. So do the sloppier versions people actually type: i need more fish, give me more fish, i want more fish, please more fish. All of them add to the shoal.
Keep going and it gets crowded fast. Somewhere past forty the water stops looking like an ocean and starts looking like a very bad aquarium, which is its own kind of funny.
The bigger thing
There’s a second command that sends something considerably less friendly through the tank. It doesn’t eat anything, it just cuts across and scatters the shoal, and the fish take a good ten seconds to regroup. Try it once when there are plenty of fish in there. It’s better with a crowd.
Bubbles are pure decoration
No effect on anything. They just look right. Turn them off if your laptop fan starts complaining, because the bubble layer is the only expensive part of the whole scene.
Spelling this is a nightmare
Onderwater, andar water, under the water, underwater sea. People type all of it and still land on google underwater, because the search engine is more forgiving than any of us deserve.
Similar moods
This is the calmest thing on the list, which puts it near let it snow google and floating google rather than anything with a score. Google gravity is the aggressive opposite, and google matrix swaps the water for falling green characters.
Full shelf: google easter eggs.