Iowa Admin. Code r. 571-41.1
"A display area" is the area on a sign or buoy needed for display of a waterway marker symbol.
"Buoy" is any device designed to float which is anchored in the water and which is used to convey a message.
"Regulatory marker" is a waterway marker which has no equivalent in the U.S. Coast Guard system of navigational aids.
"Sign" is any device for carrying a message which is attached to another object such as a piling, buoy, structure or the land itself.
"State aid to navigation" is a waterway marker which is the equivalent of a U.S. Coast Guard aid to navigation.
"Symbols" are geometric figures such as a diamond, circle, rectangle, etc., used to convey a basic message.
"Waterway marker" is any device designed to be placed in, on, or near the water to convey an official message to a boat operator on matters which may affect health, safety, or well being, except that such devices of the U.S. or any agency of the United States are excluded from the meaning of this definition.
Iowa Admin. Code r. 571-41.1