The discharge of raw untreated sewage is illegal in all US waters inside the "3 mile limit" (9 miles in the FL Keys). The discharge of TREATED waste from a CG certified Type I or II MSD (treatment device) is legal in all US waters except those water specifically designated "no discharge" (mostly inland lakes, but also a few coastal areas). It is legal to flush the toilet directly overboard outside the "3 mile limit." However, the "3 mile limit" does NOT mean 3 miles from the nearest shore in a harbor, lake or bay...you must be in open ocean at at least 3 miles from the nearest point on the whole US coastline or any island.