Intertidal Survey Mapping (phase 1) from Pen-ychain to Criccieth, Pen Llyn a'r Sarnau Special Areas of Conservation (SAC) 2010 dataset https://portal.medin.org.uk/portal/start.php?tpc=007_NRW_DS113087 The Habitats Directive establishes that the management of Special Areas of Conservation (SACs) should aim to achieve the favourable conservation status of habitat and species features listed within its Annex I and Annex II. For SACs in Wales, the Countryside Council for Wales (CCW) is therefore required to report on a regular basis on whether features are in favourable conservation status. The purpose of this data capture was to conduct a habitat survey of the intertidal area from Pen-ychain to Criccieth Castle on the south coast of the Llyn Peninsula. This work supported the detailed SAC monitoring program by providing a more up to date baseline survey of the intertidal area. It provided CCW with information to help deal with current and future casework in relation to coastal defence, and reporting particularly regarding BAP habitats and species of conservation concern. One such Biodiversity Action Plan (BAP) habitat are the Sabellaria alveolata reefs which are formed by the honeycomb worm Sabellaria alveolata, a polychaete which constructs tubes in tightly packed masses with a distinctive honeycomb-like appearance. These reefs can be up to 30 or even 50 cm thick and take the form of hummocks, sheets or more massive formations. Reefs are mainly found on the bottom third of the shore, but may reach mean high water of neap tides and extend into the shallow subtidal in places. The current report aims to fill these knowledge gaps for the survey area. The purpose of this data capture is to update previous intertidal mapping in the area and to specifically provide an updated extent of honeycomb worm reef Sabellaria alveolata. The specific project aims were to identify natural temporal changes that have been witnessed since the original Phase 1 Intertidal Mapping Project in 1996-1997. 20110131