Summary and Background Part 2: Exclusive Economic Zone, Uk Marine Area and Welsh Zone Section 42: UK marine area
133.This defines the geographical area referred to elsewhere in this Act for the purposes of managing the United Kingdom’s maritime space. It includes those areas of the sea and seabed over which the United Kingdom enjoys sovereignty in addition to those offshore areas over which the United Kingdom is able to assert its sovereign rights.
134.Subsection (3) describes the landward limit of the marine area.  Subsection (4) adds further detail to the meaning of subsection (3)(a) by providing that areas that would be open to the regular action of the tide, apart from the fact that they are generally isolated from it by an artificial barrier such as closed lock gates, but where seawater may flow or be caused to flow (as, for example, by pumping), are part of the UK marine area.  Such areas include harbour basins that are never or rarely open to the tide, such as at Bristol Harbour, but which contain seawater.