124.Section 20 amends section 53 of the 1979 Act (monuments in territorial waters) to clarify the circumstances in which a monument in territorial waters is to be treated as being in Wales for the purposes of the Act. New subsection (2B) states that a monument in territorial waters is not to be treated as being in Wales unless it is situated in Wales as defined in section 158 of the Government of Wales Act 2006. This definition of Wales includes the sea adjacent to Wales out as far as the seaward boundary of the territorial sea.