River Race was an old arcade game that AJ deleted back in the day (lol idk when it was) but was never fully removed from the game. I only know of two people who have this game and no I'm not telling you who they are.
 
I really don't know why AJ deleted it. It's really fun, can be played with multiplayer with 4 people or by yourself, and still has the achievements for playing it. 
 
Basically, you use the arrow keys on your keyboard to move your boat around, each boat having a different colour flag. You dodge obstacles like whirlpools and rock and try to aim for the green arrows which allow you a small burst of speed. 
 
So pretty much it's Wipe Out (the video game not the show), Falling Phantoms and Wind Rider all in one. Here are some snaps:
 
 
As you can see from the above 4 pictures, you earn 6 times more gems if you win in Multiplayer mode than in Single Player mode (wow did I just do maths on the weekend that is sad)
 
Here's an achievement you can get from River Race I think after playing 10 games? May will have to confirm this for me if you're reading. Maymaymaymay, may. 
 
May.