The eastern and southern boundaries of the Southeast region of the United States are formed by the following bodies of water:

* East: The Atlantic Ocean forms the eastern boundary.

* South: The Gulf of Mexico forms the southern boundary.

It's important to note that the Southeast region doesn't have a specific, universally agreed-upon boundary. It's generally understood to include states like Florida, Georgia, South Carolina, North Carolina, Alabama, Mississippi, and sometimes even parts of Tennessee and Virginia.