Micronations/Starting your own micronation/Independence
The basics of independence
If you own land, have a government, and a constant population, you're classed as a nation according to international law. However, you are only recognized as an independent nation when enough current nations agree that you are.
The closest nation is the biggest hurdle. They'll probably think that since they have more, and bigger, weapons than you, that means they can own your island.
If you can get them to accept that it's sovereign, you've got a good chance of success. You might even get their help convincing the rest of the nations to leave your tiny little island nation alone. Treaties are usually mutually beneficial.
Note that nations don't like the idea of new nations sprouting up all over. Not only does it make world politics more confusing, it's not in their interest to recognize new nations, as a new nation would have equivalent rights to these existing nations.
Avoid aggravating other countries
In case you decide to build your own island nation, a good idea is to make sure that your island is placed in international waters before you declare independence. Avoid attention from other countries as your country is probably defenseless against any military and will have only a small population to defend itself.
Who Owns the Ocean?
- Internal Waters: These are any bodies of water that are above the low-tide mark, such as rivers and deep bays. You can do anything here. These are within your territory in all respects, and you can expel other countries' ships from here even if they do not pose a risk to you because anyone passing within these waters without express permission is trespassing. (However, some countries have agreed to allow ships free passage through some rivers to allow landlocked countries access to the sea.)
- Territorial Sea: 12 nautical miles about your territory, you can do anything you want, most notably harvesting minerals and fishing. Any other countries' ships can pass through without danger, as long as they do not threaten you in any respects. You can regulate other countries' ships' activities here. You can expel other countries' warships, but in peacetime that is usually considered unnecessary.
- Contiguous Zone: Another 12 miles past the border of the territorial sea, you can enforce your customs, immigration, and sanitation in this area. You can also engage in Hot Pursuit, or chasing lawbreakers.
- Exclusive Economic Zone (EEZ): You can do any kind of fishing and mineral exploration here. You are trusted to use it wisely. This zone extends as far as 200 nautical miles, making exceptions for countries that are closer together. All natural resources in this area are yours and yours only, unless agreements have been made to the contrary.
- The High Seas: This extends beyond the EEZ, and anyone can do anything here, unless it is prohibited by international law. That is why merchant ships carry guns. The mineral resources out here are for anyone that can extract them.
Note though, that there still exist international laws against piracy. Essentially, if you commit piracy, you can be attacked wherever you may be. Some countries may use this as an excuse to attack you without warning, claiming that your declaration of independence is an act of piracy.