Grey seal at Strumpshaw?

Hi, I have just joined as I wanted to ask has anyone else seen a grey seal at Strumpshaw?  My husband, son and myself were walking along the river bank about 4.30 yesterday; I was watching a small boat motoring towards the coast towing something behind it...only to recognise it as a grey seal which seemed to be following the boat going towards the coast.  Seals are marine mammals; is it unusual to see one so far inland?