Oil and water do not mix, anyone can tell you that.
It is a basic rule of science, which certainly holds true in the jungles of northern Peru, at the headwaters of the world's greatest river system.
Not for the first time in recent years, locals have been dealing with the aftermath of a huge oil spill after a trans-Amazonian pipeline fractured, emptying some 3,000 barrels of thick black crude into the jungle river system.
For the last month, workers from Peru's state-controlled petrol company have been mopping up and scooping up much of the oil that stuck to the ravines and vegetation in the smaller rivers.
No one really knows how much was swept down the River Chiriaco and then into the River Maranon, one of the biggest Amazon tributaries in Peru.
Nonetheless, officials from PetroPeru were keen to tell us how well the clean up was going.
The man in charge of the operation is Victor Palomino. He is showing us how thousands of sacks loaded with contaminated earth are being collected and removed for disposal.