Yes, the oceans are included in areas that can become monuments. Monuments can be created out of areas that lie offshore, so long as they lie within the US Exclusive Economic Zone, which extends 200 miles from shore. The Supreme Court upheld a marine expansion of California’s Channel Islands National Monument in the 1970s, ruling that the government retained an interest in the area , despite the waters in question becoming state-owned after the expansion was put in place. And Cameron Vs Us , which held that large monuments are permitted under the Antiquities Act, remains binding precedent nearly 100 years after it was decided in 1920. The Northeastern Canyons monument lies within the Atlantic EEZ, stretching out from 150 miles out to the 200 mile boundary. Those waters are controlled by the federal government, and are considered part of the United States. areas outside of those zones are considered international waters. For instance, the deepest part of the Marianas Trench, Challenger Deep, lies within the borders of Micronesia, and thus is not included within the Marianas Trench National monument. The part of the trench that lies within US waters is included in the monument. These offshore monuments were set aside for scientific reasons, to protect the wildlife that call those areas home. Historically, there are two kinds of monuments. Historic monuments, like the Statue of Liberty, Pullman or Reconstruction Era, are small in area, they preserve buildings or objects important to US history. Scientific monuments, like Grand Canyon, Papahanamokuokea, or Mojave Trails, are large in size, in order to preserve natural formations, ecosystems, and wildlife habitat. The courts have upheld every monument ever challenged in court, regardless of size or location. There have been monuments upheld that are far larger than Northeastern Canyons. Most of Carters Alaska monuments covered at least 2 million acres, and 2 covered over 10M acres. They have consistently deferred to the president, saying their review of monument proclamations is very limited. Further, by granting the president discretion to create a monument, Congress left the size of the monument up to him. each monument is unique, some only require small areas, others need huge areas. The courts have further said they will not second-guess the president, so long as he believes a monument contains things of historic and/or scientific importance, they will take him at his word. Wyoming, Alaska and Utah have all challenged monuments, on various grounds. Not only did they lose the challenges, but the courts held they had no standing to challenge in the first place. While congress has imposed limits on monuments in Wyoming and Alaska, those limits have never been tested in court, and given Cameron remains precedent, it is unlikely those limits would survive court scrutiny. Large monuments in Alaska and Wyoming would be upheld, rendering the limits a dead letter