Setonaikai: Exploring the Seto Inland Sea of Japan

There are so many places that one can discover all over the world. These places provide so many wonders that one cannot ordinarily chance upon in their everyday life. This is why a lot of people desire to travel to other parts of the world. This is so that they get to discover more of what is out there and cannot be seen within the confinements of one’s home or office. Every country in the world has its own sets of attractions that eventually leave people in awe of how nature works. Among the many countries that have a lot to offer in terms of this is none other than Japan.

Aside from being the home of anime and manga, Japan is also known to be the land of such beautiful creations of nature. With its beautiful mountains and historical shrines, the Land of the Sun can be considered as a must-visit for travelers all over the world. Among its greatest attractions that one believes need to be visited when in Japan is the Seto Inland Sea.

Seto Inland Sea: Map, Geographical Features, and Waterways

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Commonly known as the Setonaikai in Japanese, the Seto Inland Sea is a body of water that separates three of the four main island of Japan. These three islands are known as Honshu, Shikoku, and Kyushu. Also called Setouchi or just Inland Sea, the Seto Inland Sea is located at the Pacific Ocean. With the coordinates of 34° 10’ N 133° 20’ E, the surface area of Setouchi is 23,203 square kilometers, which is equivalent to 9,000 square miles.

A region known as the Setouchi Region occupies the Seto Inland Sea and the coastal area of the three mentioned islands of Japan. Seoutchi also functions as a waterway that connects the Sea of Japan to the Pacific Ocean. Furthermore, it also connects to Osaka Bay and serves as a link of transportation to the Kansai region, wherein there are industrial centers such as in Osaka and Kobe. Moreover, it also served as the main link of transportation between Kyushu and Kansai prior to the completion of the San’yo Main Line.

There are also several prefectures that have coastlines on the Seto Inland Sea. These prefectures include Hiroshima, Hyogo, Wakayama, Ehime, Fukuoka, Yamaguchi, Okayama, Osaka, Kagawa, Tokushima, and Oita. In addition, the cities of Iwakuni, Matsuyama, Hiroshima, and Takamatsu are also situated on the coastlines of Seto Inland Sea. With considerably low levels of rainfall, the Setouchi region is known to have only moderate climate. Among its acclaimed fame throughout the country is its periodic red tides known as akashio in Japanese. This is the effect of heavy groupings of specific phytoplankton that cause the death of huge numbers of fish.

The Seto Inland Sea itself is 450 kilometers in length measuring from east to west, which is equivalent to 280 miles. From south to north, its width changes from 15 kilometers to 55 kilometers, which is equivalent to 9.3 miles and 34 miles, respectively. The depth of the water is relatively shallow with only an average of about 37.3 meters deep, which is equivalent to 122 feet. The deepest the water has gone is 105 meters, which is equivalent to 344 feet.

What acts as the main connection of the eastern part of the Seto Inland Sea to the Kii Channel is the Naruto Strait. Through the Kii Channel, the Seto Inland Sea is then connected to the Pacific Ocean. As for the western part of the Inland Sea, it connects to two places, namely, to the Sea of Japan via the Kanmon Straits and to the Pacific via the Bungo Channel.

Every part of the Setouchi has its own individual names in Japanese. An example of this would be the name Iyo-nada, which represents the strait among three prefectures located in the western part of the sea. These three prefectures are Yamaguchi, Oita, and Ehime. On the other hand, the name Aki-nada refers to the open expanse that is located near Hiroshima prefecture, just west of the Geiyo Archipelago. Another example would be the name Suo-nada, which represents the expanse just between Suo-Oshima and Yamaguchi prefecture.

The Setouchi has almost 3,000 islands, consisting both major and minor ones. The major islands on the eastern part of the sea are Shodo Island, Naoshima Islands, Awaji Island, Ieshima Islands, and Shiwaku Islands. As for the central part of the sea, there are Innoshima, Hinase Islands, Omishima, Kasaoka Islands, and Itsukushima, which is more commonly known as Miyajima. Last but certainly not the least, the western area of the sea contains Uwakai Islands, Suo-Oshima, and Hashira-jima Islands.

More than 500 marine species are known to reside under the Seto Inland Sea. These include an amphidromous fish, the finless porpoise, the ayu, the hourseshoe crab, and the great white shark, which was known to have attacked some people on certain occasions. Whales previously entered the Seto Inland Sea to either feed or breed but these activities have ceased to exist due to whaling and pollution.

History Behind the Seto Inland Sea of Japan

The history behind the Seto Inland Sea dates back to the last ice age, wherein it was believed that the sea level at that time was lower than its sea level at present day. However, the Seto Inland Sea only formed after the ice age when seawater discharged into a basin located between two mountains, namely, the Chugoku mountains and the Chikoku mountains. The Seto Inland Sea functioned as a major transport line between its coastal areas as well as between Japan and other countries such as China and Korea. The Setouchi also remained a primary transport route even after the completion of other major highways like the Nankaido and San’yodo.

To encourage trade between the country of Japan and the Song dynasty of China, it was planned that the capital be moved from Kyoto to the coastal village of Fukuhara, which is now known as Kobe, by Taira no Kiyomori during the 12th century. However, this plan was wavered and Kyoto remained the capital. Later on, the Battle of Yashima occurred just off the coast of what is now known as Takamatsu.

However, navies known as suigin in Japanese from regional powers took over most of the coastal area of the Seto Inland Sea during the feudal period. For those who are not aware, suigin directly translates to “water army,” which were considered public enemies for a certain period of time. Among the famous suigin lords at the time were the Kono clan in Iyo Province, which is now known today as Ehime prefecture, and the Kobayakawa (later known as Mori) in Aki Province, which is now known as a portion of Hiroshima prefecture.

On the other hand, the Seto Inland Sea became among the busiest transport lines in all of Japan come the Edo period. Through the Sea of Japan, the Seto Inland Sea became a part of a navigational route around the islands of the country. Not only did it serve as the main transport line between Kyushu and Kansai but also Tohoku, Hokuriki, and Hokkaido. In addition, the Setouchi also became a part of the official Chosendentsushi route, which brought emissaries from Korea to the Shogunate.

Industrialization came upon the coastal cities of the Setouchi after the Meiji Restoration. Land transportation developed since the Meiji period, which decreased the importance of the Setouchi as a transport line. Nonetheless, the Seto Inland Sea is still being used up to this day by an international cargo transport line as well as local transport lines that connect Honshu to Kyushu and Shikoku.

Transportation: Pilotage and Bridges in Seto Inland Sea 

By Leo-setä (originally posted to Flickr as Japan) [CC BY 2.0 (], via Wikimedia Commons

Currently, there are two main purposes for the Seto Inland Sea to serve its coastal areas. These two reasons are for domestic or international transportation of cargoes and for local transport among coastal areas and islands located on the sea. Major ports that use this service include Okayama, Tokushima, Hiroshima, Kobe, Takamatsu, and Matsuyama.

Furthermore, there are also three series of bridges that connect both Honshu and Shikoku since the late 1980s. From east to west, these bridges are the Akashi Kaikyo Bridge, the Great Seto Bridge, and the Nishiseto Expressway. Collectively, these three bridges are known as the Honshu-Shikoku Bridge Project due to its purpose of connecting the two islands. However, there is no bridge that connects Kyushu to the other islands over the Setouchi.

Tracing back to the history of the Seto Inland Sea, it has served as a transport line for four coastal areas. These coastal areas are Chugoku, Kansai, Shikoku, and eastern Kyushu. Local transportation was provided to each of these regions, along with the connection to other and far areas that include the coastal area of the Sea of Japan, China, and Korea. The role of the Seto Inland Sea further progressed, as it became a primary international waterway that connects to the Pacific when the Kobe port was established to serve foreign ships back in the year 1868.

Development was made wherein travel between the eastern part and the western part of the Inland Sea was shifter to railroad and road transport. Two coastal railways were constructed, namely, the San’yo Main Line located in Honshu and the Yosan Main Line. These railway lines served as a catalyst to improve the local economy at the time.  Train ferry lines that connected Honshu and Shikoku were also established by the Ministry of Railroads and, later on, the Japanese National Railways and the Shikoku Railway Company. These ferry lines also included Uno Station in Tamano and Takamatsu Station in Takamatsu. However, this ferry line ceased to operate upon the completion of the Great Seto Bridge.

Travel and Tourism: Tours, Cruises, and Revenue Due to the Inland Sea

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Considered as one of the most popular tourist destinations of Japan, the Seto Inland Sea has received praises from key people of the Western world who have visited the Setouchi. These key people include Philipp Franz von Siebold, Ferdinand von Richthofen, and Thomas Cook. Furthermore, the coastal area of the Seto Inland Sea, apart from Osaka prefecture and a portion of Wakayama prefecture, was designated as the Setonaikai National Park on the 16th of March in the year 1934. Also known as Setonaikai Kokuritsu koen in Japanese, it is considered as among the three oldest national parks in the country.

Another famous tourist site in the Seto Inland Sea is the Itsukushima Shrine located at the city of Hatsukaichi in the island of Itsukushima. Designated as a UNESCO World Heritage Site, this shrine is one of the most well-known Japanese sites that is located outside of Kyoto and Tokyo. Other famous tourist sites include Shodoshima and the Naruto whirlpools.

Because of how popular the area is, there are several local tours and cruises that set trips to the Seto Inland Sea. This generates great revenues for the many islands in the area and consistently boosts the local economy. Among the popular Inland Sea cruises are SKK or Seto Naikakai-kisen cruises. The price for availing these cruises can range from 7,000 yen to 12,000 yen.

Why Exploring the Seto Inland Sea is Highly Recommended

There are many reasons as to why one should explore the Seto Inland Sea. For one, it is where some of the best art pieces in Japan can be seen. Specifically, one should visit Naoshima, as it is an island that is dedicated to the soul of art. Commonly known as the “art island,” it can be easily accessed in just 20 minutes by ferry from Uno, Okayama. Some of its key attractions include Chichu Art Museum, Benesse house Museum, and the Art House Project.

Other activities that one can do when exploring the Seto Inland Sea include cycling the Shimanami Kaido, discovering the Japanese horticulture, and kayaking around the iconic shrine located on the island of Miyajima. Exploring the towns in the different islands of the Seto Inland Sea is also highly recommended. Truly, there are several ways to explore the Seto Inland Sea and doing so would definitely be worth it.