The Coastal Marine Area is the foreshore, seabed and coastal water, and air space above the water of which the seaward boundary is the outer limits of the territorial sea and of which the landward boundary is the line of mean high water springs except that where that line crosses a river. The landward boundary at that point shall be whichever is the lesser of one kilometer upstream from the mouth of the river; or the point upstream that is calculated by multiplying the width of the river mouth by 5.
