There are hard and soft corals in the Gulf of Maine and extending along the eastern seaboard of the U.S.
They have been the subject of debate in the Mid-Atlantic and Gulf of Maine regions. Here is some of the information about where they are:
Gulf of Maine: The State of Deep Coral Ecosystems of the United States, Chapter 5 Northeast (2007)
Coral and Sponge Concentrations in the Biogeographic Regions of the East Coast
of Canada Using Spatial Analyses (2010)