With many thanks to JonTheNaturist who has visited this beach...
It is known to *some* locals as "the nudist beach" but does not seem to be well used as such. It is very quiet.
It should be noted that last time I was there in late 2020, the Church car park was closed. That might have been lockdown related. Without it, parking is quite limited. The only vehicular access is down Fort Road, off the main road between Sully and Penarth. There is some parking at the end of the road, by the Church.
Radio buffs will note the Blue plaque by the lychgate, marking the fact that this is the spot from which Marconi sent the world's first radio signal across open water, to Flat Holm island (visible from the beach). There is a busier coastal path nearby with WWII gun emplacements. Walking to Penarth Pier is not arduous, but better done clothed.
The Beach is tidal - You really need to go when the tide is well out. There are occasional walkers, with and without dogs. Also some geology students looking for interesting rocks once! Although people did walk some reasonable distance from me, there was no indication of surprise or annoyance. At low tide the beach is very large.
Access is down a fairly overgrown path. Nettles abound, so take care. The entrance to the beach is not for those with mobility issues. You can walk from sully along the beach at low tide, but it is rocky and hard going. I have attached some photos.
The Beach is just rock. There is no sand to speak of. The water is murkier here than it is by Kenfig and Monknash, but people do paddle and bathe sometimes. It is OK for a sit down and a picnic, perhaps, but 30 minutes up the road is the much nicer Monknash Beach. Kenfig is another sandy alternative. Both involve a much longer walk, however, and are further from shops and facilities.