Flood servers are always really dumb, because everyone just builds a bunch of poles going straight up. This should be fixed by having AI in the water that can destroy bricks and damage players. That way, you have to link up and repair your supports. You shouldnt be able to build more than 64 bricks away from your current position, and the water should have oxygen/death. This encourages people to use submarines to travel and fix their supports.
It would get harder as the water goes up, as you will have to go farther down in order to repair your supports.