The natural freshwater pits at Dungeness, with their Transition Mire communities are thought to be unique to Dungeness, but the geomorphological processes that formed them are not, and at Rye Harbour there are similar, though younger features near the Lifeboat Station that show an earlier stage in the development of these sorts of wetland communities. All of these ponds formed as shingle ridges developing along the shoreline left low lying hollows that became open water lagoons. They are very rare natural features, primarily because shingle beaches themselves are a rare habitat, and are much more interesting than the artificial gravel pits that disfigure these shingle habitats.
Being closer to the sea the Rye pits still show a brackish influence, demonstrated by the presence of sea club-rush Bulboschoenus maritimus and bulrush Scirpus tabernaemontani. There are also stands of narrow-leaved reedmace Typha angustifolia and common reed Phragmites australis. Although they are not as large as some of the Dungeness pits, nor as botanically diverse they are valuable in showing the early development of these habitats. They compliment the more middle-aged freshwater Oppen Pits on the RSPB reserve and the ancient saline pits that are eroding back into the sea on Lydd ranges and all of them illustrate the process of natural development of these habitats over time.