In Okinawa the sea has much to offer, and it is astoundingly beautiful—so beautiful that one local word for “sea,” chura umi, includes the nuance, “beautiful and clear.” It would be hard to imagine life in Okinawa without the sea. If you visit, you will certainly be captivated by its natural beauty.

Sandy formation called Hate no Hama, east of Kume-jima Island.

The color-coordinated coral reefs and the tremendous diversity and density of marine life astound me every time I go to Okinawa. The first time I went there I was a student, and I have been back every year since, for more than 30 years, drawn to the sea around Okinawa’s many islands.

Okinawa Prefecture, in the far southwest of Japan, is a chain of islands consisting of several island groups, the most notable being the Okinawa, Miyako, and Yaeyama groups. The island chain, called the Ryukyu Archipelago, traces a line between the Pacific Ocean to the east and the East China Sea to the west. On the Pacific Ocean side, the Kuroshio Current flows in from the south through the island, creating warm conditions for many marine species and some of the world’s best coral reefs. The Kerama Islands, also part of the archipelago, are known worldwide for the underwater beauty of their coral reefs.

The large coral reefs that are common in Okinawa are not found further north, of course, but they are not seen further south either. There are several reasons for this:

• The Okinawan islands are situated some distance from Asia’s continental landmass, so the marine environment is free of the vast quantities of silt and organisms that the continent’s rivers wash into the sea. The seawater is so clear that you can see 40 to 50 meters below the surface. The sun shines strong and deep into the water, providing the necessary conditions for reef-building corals.
• Because there are no large rivers dumping freshwater into the sea, the salt content of the seawater is high enough for coral growth.
• The Kuroshio Current brings water from the tropics. The climate is subtropical, unusual for such relatively northern latitudes.

These conditions give the sea around Okinawa a wide variety of corals and help to build large coral reefs.

As you may know, corals and coral reefs are different. The seawater off Southeast Asia has corals, but no major coral reefs. Corals are living organisms called cnidarians, and they exist either as solitary creatures or as members of colonies. The reefs are a mass of reef-building corals and dead, calcified organisms with bones or shells—everything from coralline algae and foraminifers to shellfish. Through hardening processes occurring over a long period of time, they form the underwater topography we see today.