Contrary to what the common name may lead you to believe, swamp cancer is not a cancer, but is caused by an aquatic fungus. The disease is called Pythiosis and is caused by the organism Pythium insidiosum.
It is a plant parasite that causes an infection of the skin and can quickly cause large lesions with devastating consequences. It normally lives on water vegetation or organic debris in tropical and sub-tropical climates. Other common names are “summer sores” and “phycomycosis”.