A photo of the seal was snapped in passing by Stockton Heath resident Norman Goodhand.
He spotted the seal on the banks of the River Mersey close to Marshall Gardens near the town centre on Saturday.
Seals mainly turn up in town rivers because they are following food, exploring, or using sheltered spots to rest, and cleaner urban rivers now make that possible.
Seals are naturally inquisitive and will explore estuaries, harbours and rivers, including built‑up areas, if there’s food and relatively little disturbance.
Resting in sheltered water: Urban rivers and docks can offer calm, sheltered places to haul out and rest between feeding trips, especially in estuaries and tidal reaches near towns.
Seals have been spotted in the Mersey in Warrington on a number of previous occasions, but they are always a delight to see.