The river is a navigable tidal estuary from Newport northwards, where it takes the form of a ria (a drowned valley).

As the Solent valley flooded, the river received less water and more sediment, causing it to become more tidal.

The navigation of the river was improved in the nineteenth century by Henry Daniel Martin, a civil engineer who lived in Newport.

Along its banks there are old warehouses and wharves, where in the past flying boats, hovercraft and steam ships were developed and built.

The Island Harbour Marina, at the site of an old tidal mill, is on the river about two miles from Newport.