Submerged forest - Swansea Bay and Gower

Swansea Bay -- foreshore in front of Singleton Park (3 photos)

I found some nice pics of the submerged forest around Gower and in Swansea Bay -- on Adam Tilt's blog:

https://www.mylifeoutside.co.uk

These next 3 photos are from Broughton Bay:

Adam says that there are similar exposures in Port Eynon, Whiteford and elsewhere......  Not much peat, by the look of it, but a lot of estuarine mud......

But this is a curious feature on Whiteford Sands.  Looks like a bomb crater (it's 8 ft in diameter) with a thinnish layer of peat or peaty silt thrown up around the circumference.....  What is it?  Answers on a postcard please........

Submerged forest exposures, Whiteford Sands (photo: Pembs Coastal Photography)