Baselines are essentials to the delimitation of maritime boundaries. The common regime of the normal baseline under the article 5 of the United Nations Convention of the Law of the Sea (UNCLOS) defines the normal baseline as the low water line along the coast. Furthermore, UNCLOS allows coastal States to use straight baselines under certain situations. Also, UNCLOS offers a large range of possibilities for States (for bays, ports, reefs, etc). States should define and often precises the UNCLOS regime under their legislations and/or regulations (they should determine which types of baselines they will choose and how they will determine it). The shape of the coastline in any given locality can differs and consequently UNCLOS allows States to use different types of baselines (article 14 of UNCLOS). States generally uses normal and straight baselines. However, the types of baselines and the methods are chosen, and the physical changes of the coastal state can represent a challenge for States which can be the case for Australia, France, some Pacific Islands states, and China.