Guatemala's Lake Atitlan was once one of the most threatened water bodies in the world. Decades of pollution had spoiled the waters, with an algae bloom covering nearly half its surface.
Tourism plummeted and the government promised to do more to protect the lake.
Four years on, money is not the issue: $100m has been earmarked for water and sanitation projects. Authorities are planning to have seven fully functioning waste-treatment plants in place by 2016.
Al Jazeera’s David Mercer returned to Lake Atitlan to report on the change.