In the heart of Carnac-Plage it is uncertain if this is truly a prehistoric monument. Burl does not include it in 'Megalithic Brittany'. However it is included in Gabriel Le Cam's monumental 'Le Guide de Megalithes de Morbihan', he calls them:
"A dolmen and menhir that are certainly not in their original location"
Although the dolmen is super-sterotypical but not, on closer inspection, much like anything else around here, the stones themselves have an air of 'ancientness' and do not have the quarry marks and boreholes of many recently erected megaliths.
It could just be that these stones once formed an ancient monument, although whether this was their form is open to debate...