Also they cannot be destroyed or captured. Around these you will be able to collect boxes of money.
Closer to the center of the map are drop zones. There are two zones between the players on which after the waves will appear unnamed vehicles. There are 'radar houses' on the map that give you a mini-map as well as a glimpse of some parts of the map. You can also see from the textures where the water will stop. On the bottom right you will see a timer, after which the water level will rise by one level.
The idea is to constantly get closer to the center of the map while the edge of the map is flooded with water.
