A man has died after his car crashed into the Slapton Ley near Kingsbridge – the largest lake in south west England.
Police divers are currently searching the sunken vehicle and the surrounding area to rule out further casualties.
Devon and Cornwall Police said emergency services were called to the nature reserve at Torcross just after midnight after receiving reports of a car had travelled across grassland and had come to rest in the water.
On arrival paramedics treated the driver but he was pronounced deceased at the scene a short time later.
Formal identification has not yet taken place, although next of kin are being informed.
A spokesman from Devon and Cornwall Police said: "Officers from the Force Serious Collisions Investigation Unit have conducted an examination of the scene and are investigating the circumstances of the collision."
The A379 was closed but reopened around 7.20am today.
Slapton Ley is a lake on the south coast of Devon that is separated from Start Bay by a shingle beach, known as Slapton Sands.