A second search of the Clutha River is under way for a missing Dunedin teenager.
The 16-year-old was swimming with a friend below the Roxburgh Dam on Tuesday afternoon when he got into difficulty and disappeared.
Police say the river has been lowered by restricting the water flow through the dam.
They believe the boy may have become trapped in debris.
Locals describe the spot where he disappeared as treacherous, with strong swirling currents and whirlpools which can suck swimmers below the water.