Ares Macrotechnology - Most of Ares's public installations are on the surface of the Great Lakes and the Eastern Seaboard. Several are oil drilling platforms. One notable group of platforms is the Sigsbee Plain Platforms west of Florida in the deepest part of the Gulf of Mexico. Ares also owns a deep sea aquacology, called the Ares Trident Aquacology, which by some reports predates the Yamatetsu Saotome AquaDomes by 2 years.
Proteus AG - The big AA Megacorporation name in oceanic habitats, Proteus AG has been building offshore facilities and arkoblocks for some time, and represents the major public competition with Yamatetsu.
Renraku - Renraku's Underwater Living project has been plagued with problems. Underwater Living is primarily submerged fisheries along the Phillipines, and was building an underwater 25 square kilometer domed city. Originally based on the SCIRE and set to go on-line in 2065, the Underwater Living aquacology was shut down for safety concerns for a year after the Seattle arcology shutdown, and then it was damaged secondary to magical effects of Halley's Comet on the Pacific Rim. The city is heavily armed and armored "for safety concerns". Underwater Living also has a deep sea facility 1,500 meters down in the Java Trench.
Saeder-Krupp - S-K maintains two underwater training facilities for their aerospace program and dozens of mining platforms in the Baltic Sea. It has an experimental self-sufficient mining colony in the Iberian Abyssal Plain called the Cadmus Deap-Habitat Colony. It is likely they have more facilities in other locations.
Shiawase - Shiawase Atomics holds several hydroelectric and geothermal power facilities throughout the Sea of Japan, making Shiawase the Pacific Rim's major power supplier. Its subsidiary Kuroyama Minerals is another part of Shiawase's offshore development. Shiawase also owns several offshore mobile research facilities, including the Arboritech Vanguard Station.
Yamatetsu - The leader among the AAA Megacorporations in aquatic facilities, Yamatetsu won the Draco Foundation prize for building the first self-sustaining aquatic colony through its Saotome AquaDomes. They also are planning for their Kuorshio Offshore Power Plant. They are also undertaking a project called the Drake Passage Dam project, which will be located between the southern tip of South America and Antarctica. Yamatetsu's surface-related efforts include its Vladivostok shipyards, shallow-water mining, and power plants. Yamatetsu also has several mobile mining platforms in use across the Pacific.