Except when the grant under which the land is held indicates a different intent, the owner of the upland, when it borders on a navigable lake or stream, takes to the edge of the lake or stream at low water mark. All navigable rivers shall remain and be deemed public highways. In all cases when the opposite banks of any stream not navigable belong to different persons, the stream and the bed thereof shall become common to both.
N.D.C.C. § 47-01-15