The current marine boundary in OSM uses bot generated 12nm circles which does not always correctly show the proper international boundary which is reached by an international treaty.
The international Boundary Commission lists the actual marine boundary between Canada and the US.
http://internationalboundarycommission.org/products.html#maps The boundary by Maine needs to be updated.
Also, the Canada / St. Pierre Miquelon boundary needs to be updated from the bot generated lines. http://www.state.gov/documents/organization/61505.pdf
The US State department has a good list of resources for marine boundaries all over the world. http://www.state.gov/e/oes/ocns/opa/c28187.htm
Looking at the current map, some marine boundaries show the 200 mile Exclusive Economic zone, while most of the world shows the robot generated 12 nm line.