The Humber is the tidal estuary from which Pilgrims (very likely including Bradford) made their escape to Holland.

The traditional location for their escape is inside a large commercial port which is not open the public. This monument was moved to a publicly accessible park
We headed to a different site on the Humber, another possible site they departed from. The large mud banks here are because we visited at low tide.
This certainly gives a better impression of what the landscape looked like in the 1600s than the commercial port.