A wake is defined as a movement of the water created by a boat underway great enough to disturb a boat at rest, but under no circumstances shall a boat underway exceed 5 miles per hour while in a posted “No Wake” area. “No Wake” areas shall be clearly posted with buoys or appropriate signs except as provided in Section 5-7 of this Act. All buoys or signs posting “No Wake” areas shall meet the specifications as prescribed by the United States Coast Guard or the Illinois Department of Natural Resources.