Sec. 1.5. As used in this chapter, "lake" means a reasonably permanent body of water that:
(1) existed on March 12, 1947;
(2) is substantially at rest in a depression in the surface of the earth that is naturally created;
(3) is of natural origin or part of a watercourse, including a watercourse that has been dammed; and
(4) covers an area of at least five (5) acres within the shoreline and water line, including bays and coves.