Seastead Basics: Building On a Foundation

Above, you can see the basic "Clubstead" design from Seasteading.org, and one final design using the basic concept as a foundation. Your choice of foundation will pre-determine much of your final design.

The Clubstead is built upon four vertical pontoons, one at each corner. This is similar to many oil drilling platform designs, and seeks to minimise the cross-section to oncoming waves.  Wind exposure can be significant, however.   Failure of the structure can be catastrophic should sustained waves exceed the design parameters.
Above you can see the "Lilypad" design from Vincent Callebaut Architectures of Belgium.  It features a central bowl-shaped hull which is augmented by supporting flotation located about the outer ring -- of an unconventional "multi-hull" variety.  This design presents a significant exposure to wave fronts, and to the wind.  Failure of this design is likely to be less sudden than for Seasteading's Clubstead -- allowing more time for occupants to escape and be rescued.

The Gyre design is an inverted seastead design -- all of the occupied real estate is under the surface. This presents very little exposure to wind and above-surface wave, but may present a greater hazard in the event of a hull breech or abandon ship situation. The deeper the pressure hull, the stronger it must be.

The Gyre offers obvious solutions for floating breakwater protection of an intrinsic harbour. The longer the outrigger arms, the greater the subsequent stresses during sustained storms. Finding the optimal material combining resilience, strength, and probably self-healing of cracks, will require some R&D.

More traditional designs based upon mono-hulls and multi-hulls offer their own advantages and disadvantages. There is a limit to how large a traditional "cruise ship" design can be built, but multiple mono-hulls can be connected in a raft-like design to form a larger structure, as long as proper measures for dealing with large waves are followed.

And then there are the quasi-absurdist designs that are meant to demonstrate an architects ability to think outside the box:

In this case, the tetrahedral New Orleans design clearly wins out over the braced rectangular Boston design, on the basis of stability alone. Imagine the topheavy Boston design dealing with heavy seas and high winds.

Most architects appear to treat the idea of a floating city as a joke, without seriously considering the raw elements of nature that must be dealt with.  It will be fascinating to watch the evolution of designs at the Seasteading Institute, and to watch for any serious competition that may appear on the horizon.