Hingham or Deopham Mere Norfolk | Unique ponds in England

Hingham Mere or Deopham Mere in Norfolk, England. One of the unique Meres of Norfolk which are special small lakes or ponds. Why are these ponds oval shape? Why are all of oval Meres of Norfolk found in a rough circle shape when viewed on the map? Are the Meres of Norfolk related to Americas Carolina Bays and the Lunettes in Australia?