Fresh and salt water meeting at the Douro river mouth, Porto, Portugal

From its source in Spain the Douro river is flowing almost 900 kilometers until it finally meets the Atlantic ocean at Foz do Douro, next to Porto.

Sitting next to the lighthouse with red and white stripes, right where the river meets the ocean, the water seems to stand still on certain moments of the tide. It looks heavy and like oil, not moving in any direction but only up and down, creating very beautiful and hypnotic but at the same time disquieting patterns.