Not really sure if this has been done before but whatever.
The Plughole
Idea of the game: Players race up a giant water stream to the top of the "bath". After 2 mins the water gets too hot and turns to lava! Players must race to the top and collect the reward in a randomized chest. They then have 10 seconds looting the chest before that area is destroyed (TNT or something, I don't know xD)
Any feedback or improvements would be deeply appreciated