Me. Rev. Stat. tit. 33, § 1213

For the purposes of this chapter, the Department of Agriculture, Conservation and Forestry, Division of Geology, Natural Areas and Coastal Resources shall draw the water boundaries of the 8 coastal counties in order to determine in which registry of deeds the island must be registered. These lines must be drawn in accordance with the corporate charters of the counties as amended. In instances in which the charter does not clearly specify the seaward boundaries of the counties, the boundaries must be drawn in accordance with state law and the principles contained in the International Convention for the Contiguous and Territorial Sea in determining seaward boundaries between adjacent nation states.