The bridge you are standing on crosses a valley. Just 10,000 years ago it would have been a typical river valley created by the passage of water in the river, as it made its way in its narrow channel from the mountains to the sea. This river had its streams and tributaries. Since then things have changed. The valley became flooded as the sea invaded. The river, its streams and tributaries all filled up deeper and deeper. It became a flooded valley with a typical shape. So now the bridge no longer crosses a river; it crosses a flooded valley. Flooded valleys are also known as Rias. Click on the Google Earth photo below to see the Pembroke area from a satellite view. Why did the sea invade this valley 10,000 years ago? This was the time when the last ice age came to an end. At that time, there was ice up to a mile thick on the land. When the Ice Age ended, the ice started to melt, the sea level began to rise, and the river valley got flooded. Rias are typical of many river valleys of southwest Wales and the south coast of England. Fjords (see the Google Earth photo of one in Norway) are also Rias. And there are also man-made rias. The Google Earth photo shows a ria far inland in Egypt, caused by the Aswan Dam on the River Nile.
To prove you have been here, answer this question: Using your GPS, what is the width of the ria where the bridge crosses it?
Also, if you can, take a photo of you with your GPS and a ria view from the bridge.