Bristol Channel is an arm of the Atlantic Ocean that lies between Wales and southwestern England. The channel extends 80 miles (130 kilometers) from the sea to the River Severn. The incoming tide sweeps up the narrowing channel, causing a bore (high tidal wave) that reverses the flow of the River Severn. The tide often rises as much as 40 feet (12 meters).
Swansea and Cardiff are the major ports on the Welsh shore. Bristol lies close to the head of the channel. Nearby, the River Avon flows into the mouth of the River Severn.
