Anyone who is present in the Dive right now can start the Game. You can only play one game at one point in time. The person who starts the game automatically becomes the host of that game.
The host has some extra powers for the games. Only they can close the game when a Dive is active. In different games, they get to start the game when everyone is available to play.
When a host leaves mid-way, the system assigns a random person as host.