As time passes some buildings will move around towards the center of the island. Build mode will be enabled/disabled every time a player is eliminated, so keep an eye out for the message that let's you know what's going on.
Choose your duo and brace for chaos. Water rises over time so make sure to get to the top of the island! Structures will move round and meet up at the top of the island, they'll link with grind rails to help you get around. Build mode will be enabled/disabled every time a player is eliminated, so pay attention to the warnings.