Seasteading is the concept of creating permanent dwellings at sea, called seasteads, outside the territory claimed by any government. The term is a combination of the words sea and homesteading. No one has yet created a structure on the high seas that has been recognized as a sovereign state.
Seasteaders say such autonomous floating cities would foster faster development of techniques “to feed the hungry, cure the sick, clean the atmosphere and enrich the poor”. Some critics fear seasteads are designed more as a refuge for the wealthy to avoid taxes or other problems.
Proposed structures have included modified cruise ships, refitted oil platforms, decommissioned anti-aircraft platforms, and custom-built floating islands.
As an intermediate step, the Seasteading Institute has promoted cooperation with an existing nation on prototype floating islands with legal semi-autonomy within the nation’s protected territorial waters. On January 13, 2017, the Seasteading Institute signed a memorandum of understanding (MOU) with French Polynesia to create the first semi-autonomous “seazone” for a prototype, but as of 2018 its status was uncertain.
Many architects and firms have created designs for floating cities, including Vincent Callebaut, Paolo Soleri and companies such as Shimizu and E. Kevin Schopfer.
L. Ron Hubbard, founder of the Church of Scientology, and his executive leadership became a maritime-based community named the Sea Organization (Sea Org). Beginning in 1967 with a complement of four ships, the Sea Org spent most of its existence on the high seas, visiting ports around the world for refueling and resupply. In 1975 much of these operations were shifted to land-based locations.
Marshall Savage discussed building tethered artificial islands in his 1992 book The Millennial Project: Colonizing the Galaxy in Eight Easy Steps, with several color plates illustrating his ideas.
Other historical predecessors and inspirations for seasteading include:
At least two people independently coined the term seasteading: Ken Neumeyer in his book Sailing the Farm (1981) and Wayne Gramlich in his article “Seasteading Homesteading on the High Seas” (1998).
Gramlichs essay attracted the attention of Patri Friedman. The two began working together and posted their first collaborative book online in 2001. Their book explored many aspects of seasteading from waste disposal to flags of convenience. This collaboration led to the creation of the non-profit The Seasteading Institute (TSI) in 2008.
On April 15, 2008, Wayne Gramlich and Patri Friedman founded the 501(c)(3) non-profit The Seasteading Institute (TSI), an organization formed to facilitate the establishment of autonomous, mobile communities on seaborne platforms operating in international waters.
Friedman and Gramlich noted that according to the United Nations Convention on the Law of the Sea, a country’s Exclusive Economic Zone extends 200 nautical miles (370km) from shore. Beyond that boundary lie the high seas, which are not subject to the laws of any sovereign state other than the flag under which a ship sails. They proposed that a seastead could take advantage of the absence of laws and regulations outside the sovereignty of nations to experiment with new governance systems, and allow the citizens of existing governments to exit more easily.
“When seasteading becomes a viable alternative, switching from one government to another would be a matter of sailing to the other without even leaving your house,” said Patri Friedman at the first annual Seasteading conference.
The Seasteading Institute (TSI) focused on three areas: building a community, doing research, and building the first seastead in the San Francisco Bay. 
The project picked up mainstream exposure after having been brought to the attention of PayPal cofounder Peter Thiel. Thiel donated $500,000 in initial seed capital to start The Seasteading Institute, and has contributed $1.7 million  in total to date. He also spoke out on behalf of its viability in his essay “The Education of a Libertarian”.
As a result of Thiel’s backing, TSI received widespread media attention from a variety of sources including  The Economist Business Insider, and BBC.
In 2008, Friedman and Gramlich had hoped to float the first prototype seastead in the San Francisco Bay by 2010 Plans were to launch a seastead by 2014, and TSI projected that the seasteading population would exceed 150 individuals in 2015. TSI did not meet these targets.
In January 2009, the Seasteading Institute patented a design for a 200-person resort seastead, ClubStead, about a city block in size, produced by consultancy firm Marine Innovation & Technology. The ClubStead design marked the first major engineering analysis in the seasteading movement.
In the spring of 2013, TSI launched The Floating City Project. The project proposed to locate a floating city within the territorial waters of an existing nation, rather than the open ocean. TSI claimed that doing so would have several advantages:
In October 2013, the Institute raised $27,082 from 291 funders in a crowdfunding campaign TSI used the funds to hire the Dutch marine engineering firm DeltaSync to write an engineering study for The Floating City Project.
In September 2016 the Seasteading Institute met with officials in French Polynesia to discuss building a prototype seastead in a sheltered lagoon. Teva Rohfristch, Minister for Economic Recovery was the first to invite The Seasteading Institute to meet with government officials.The meeting was arranged by Former Minister of Tourism, Marc Collins.
On January 13, 2017, French Polynesia Minister of Housing, Jean-Christophe Bouissou signed a memorandum of understanding (MOU) with TSI to create the first semi-autonomous “seazone”. TSI spun off a for-profit company called “Blue Frontiers”, which will build and operate a prototype seastead in the zone. The prototype will be based on a design by marine engineering firm Blue 21.
On March 3, 2018, a mayor from French Polynesia said the agreement was “not a legal document” and had expired at the end of 2017 in response to a challenger trying to make it an issue for the May, 2018 elections.
In May, 2018 Blue Frontiers began raising funds through a cryptographic token (Varyon) to prepare for building in the Sea Zone when the French Polynesian government passes the SeaZone act later in the year. 
Cruise ships are a proven technology, and address most of the challenges of living at sea for extended periods of time. However, they’re typically optimized for travel and short-term stay, not for permanent residence in a single location.
Platform designs based on spar buoys, similar to oil platforms. In this design, the platforms rest on spars in the shape of floating dumbbells, with the living area high above sea level. Building on spars in this fashion reduces the influence of wave action on the structure.
There are numerous seastead designs based around interlocking modules made of reinforced concrete. Reinforced cement is used for floating docks, oil platforms, dams, and other marine structures.
A single, monolithic structure that is not intended to be expanded or connected to other modules.
The SeaOrbiter is an oceangoing research vessel designed to give scientists and others a residential yet mobile research station. The station will have laboratories, workshops, living quarters and a pressurized deck to support divers and submarines. It is headed by French architect Jacques Rougerie, oceanographer Jacques Piccard and astronaut Jean-Loup Chretien. The cost is expected to be around $52.7 million.
Blueseed was a company aiming to float a ship near Silicon Valley to serve as a visa-free startup community and entrepreneurial incubator. Blueseed founders Max Marty and Dario Mutabdzija met when both were employees of The Seasteading Institute. The project planned to offer living and office space, high-speed Internet connectivity, and regular ferry service to the mainland but as of 2014 the project is “on hold”.
Criticisms have been leveled at both the practicality and desirability of seasteading. These can be broken down into governmental, logistical, and societal categories.
Critics believe that creating governance structures from scratch is a lot harder than it seems. Also, seasteads would still be at risk of political interference from nation states.
On a logistical level, seasteads could be too remote and uncomfortable (without access to culture, restaurants, shopping) to be attractive to potential residents. Building seasteads to withstand the rigors of the open ocean may prove uneconomical.
Seastead structures may blight ocean views, their industry or farming may deplete their environments, and their waste may pollute surrounding waters. Some critics believe that seasteads will exploit both residents and the nearby population. Others fear that seasteads will mainly allow wealthy individuals to escape taxes, or to harm mainstream society by ignoring other financial, environmental, and labor regulations.
The Seasteading Institute held its first conference in Burlingame, California, October 10, 2008. 45 people from 9 countries attended.The second Seasteading conference was significantly larger, and held in San Francisco, California, September 2830, 2009.The third Seasteading conference took place on May 31 – June 2, 2012.
Seasteading has been imagined many times in fictional works.