The harbour is largely formed by a drowned glacial valley which succumbed to sea level rise since glaciation.

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

We dreamed of its broad estuaries (drowned valleys brought back to light at low tide) and its islands (ancient hills shipwrecked off the coast).

Submergent coastlines are identifiable by their submerged, or "drowned" landforms, such as rias (drowned valleys) and fjords.

The lofty Al Hajar Mountains and the drowned valleys of Musandam are dramatic reminders of this.

Here, the drowned valleys of the Marlborough Sounds make for a convoluted and attractive coastline.

The great drowned valley that had created and framed Sydney Harbor no longer existed.

Tory Channel is one of the drowned valleys that form the Marlborough Sounds in New Zealand.

It flows generally south, with most of its length being through a drowned valley in the northeast of the Kaipara Harbour system.

It is an example of a fjard, a drowned shallow glacial valley.