The Seed Seastead is aptly named after it's shape and function.
With measurements based on the golden-ratio, it looks like an egg, potato or seed.
Here is a thread on the construction of a ferrocement-dinghy or concrete-boat of the same shape. It is 180cmx110cmx70cm or roughly 6ft by 4ft by 2ft. http://www.seasteading.org/interact/forums/research/engineering/ferrocement-dinghy
The design is highly-modular in that it can be used as a row-boat, with keel and mast a sailboat, with propeller a power-boat, with cover and windows a submarine.
one that is 4 times larger in length,height,width would fit 2 people comfortably for an indefinite period of time.
one that is 7 times larger can house 10 people.
these seed-seasteads can be attached together at sea, to make floating island.