Nate Gilman
USCG hierarchy of waters
The hierarchy of USCG waters is Oceans -> Near Coastal -> Great Lakes, -> Inland. There are some exceptions for towing and Western Rivers.

What does this mean?
From 46 CFR 11
Oceans
Subject to provisions about Western Rivers, any license or MMC endorsement for service as master or mate on ocean waters qualifies the mariner to serve in the same grade on any waters, except towing vessels upon western rivers subject to the limitations of the endorsement.
Near Coastal
Subject to provisions about Western Rivers, any license or MMC endorsement issued for service as master or mate on near-coastal waters qualifies the mariner to serve in the same grade on Great Lakes and inland waters, except towing vessels upon western rivers subject to the limitations of the endorsement.
Great Lakes
Any officer endorsement issued for service on Great Lakes and inland waters self-propelled vessels, excluding towing vessels, is valid on all of the inland waters of the United States
Inland
Any officer endorsement issued for service on inland waters self-propelled vessels, excluding towing vessels, is valid for the inland waters of the United States, excluding the Great Lakes.
We hope this made your life a little easier and if you have other questions the MM-SEAS team is always here to help!
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