The most important design criterion is that the seastead be safe in the harsh ocean environment, with its wind, waves, and currents. Thus all of these designs will need to use some of our wave avoidance techniques. Besides safety, the structure must be reasonably cost-effective, or it will never be built. Cost may well be the main barrier which has prevented people from becoming seasteaders. Its also important that the design scale well to different sizes, so that we can apply our incremental approach. Dynamic Geography tells us that physical modularity is also very desirable.