Ms Laura Brien:

Yes if one is putting any permanent structures below the high-water mark, within the maritime area. If it is a slipway, then yes. Some things are a bit more ambiguous. For example, if it was to put a boardwalk along the beach it would really depend on whether it was above or below the high-water level. Let us assume that it is below the high-water level for some aspect of the construction then one would need a maritime area consent, MAC, before going to planning.

It is one of the pieces of paperwork needed before requesting planning permission.