Wonderful nature

We spent the day in Felixstowe, never been there and didn’t know what to expect. In my head  I imagined with the docks it would be very industrial . The end we were at was in fact quite pleasant, a typical seaside town with a very nice beach, where Jak played for ages and we had a fish and chip lunch. 
The blip is from our walk along the River Orwell later in the afternoon. The base of the large tree appeared to be totally dead and rotting, but was hanging on to a collapsing bank. Someone please explain how it was still growing strong. Wonderful nature.