The Okaiyo Ocean spans the vast maritime gulf between the eastern coast of Tian Xia and the western edge of Arcadia. It is the second largest of Golarion's oceans, second only to the cold Antarkos, and sailors consider its largely unexplored open expanses quite hazardous for travel. The Okaiyo runs from pole to pole and is divided by the mighty underwater Sintos Trench.
The Okaiyo Ocean is home to abundant marine life, including large populations of fish that support fisheries throughout the ocean's extent. Char, cod, and mackerel live in colder waters towards the poles; while pike, salmon, shellfish, and tuna are found in its temperate waters. The ocean's tropical waters are home to sea bass, swordfish, and a native species of fish with three-pronged tails known as trident fish. Coastal waters are home to large, predatory shellfish known as gigas clams, which although dangerous and intelligent are sometimes pursued for their meat. A large crab spawning ground exists in the water near Minata home to millions of crustaceans, but this is often avoided due to the heikeganis that rule the area.
The floor of the Okaiyo around the Sintos Trench is the home of thousands of underwater cities of numerous races, including iku-tursos and their nomadic siyokoy rivals, as well as merrows and sahuagin. The sahuagin, in particular, rule a powerful empire from the depths of the Sintos Trench, where they live in greater numbers than anywhere else in Golarion. Their capital, called Furydeep by those who cannot pronounce its sahuagin name, is home to 10,000 inhabitants before counting the adaros, sharks and slaves who dwell there alongside the fishlike humanoids.
A flumph seedpod was recently seen crashing into the Okaiyo, nearly capsizing a fishing fleet in the process. Despite this, there have been no sightings of these strange creatures in the vicinity since then, leading some to wonder if they might have perished during their violent landing.
- James Jacobs, Dave Gross, Rob McCreary. (2011). Dragon Empires Gazetteer, p. inside front cover. Paizo Publishing, LLC. ISBN 978-1-60125-379-8
- Adam Daigle, Patrick Renie, F. Wesley Schneider, and James L. Sutter. (2012). Oceans of Golarion. Raiders of the Fever Sea, p. 66. Paizo Publishing, LLC. ISBN 978-1-60125-409-2
- Amber E. Scott and Mark Seifter. (2017). Aquatic Adventures, p. 21–22. Paizo Inc. ISBN 978-1-60125-944-8