I found this empty shell on the grass beside an inland lake in Dorset.It is quite large; my glasses are lying beside it.
No interactions present.
I found one in a similar location and wondered what had fished it out. A heron was the opinion of iSpotters.
University of Edinburgh and Biodiversity Observatory (OU)
Lat/Lng: 50.655265, -2.197423
OS grid ref: SY861839