Freshwater fungi are fungi that undergo all or part of their lifecycle submerged in fresh water. They are saprophytes which decompose fallen wood, leaves, stems, animal parts, and another dead organic matter that is in water. The are also plant pathogenic fungi, lichens, mycorrhizae, parasites, and endophytes. Fungi of terrestrial origin (and their DNA) also enter water bodies, but don’t grow or sporulate in water. We don’t consider these to be aquatic fungi.
Freshwater fungi often have specialised spores for dispersal in water, such as tetra-radiate (4-pronged), sigmoid (snake-like) spores. Many have specialised appendages or mucilaginous sheaths for attaching to substrates or vectors for dispersal such as insects and birds.
Australian freshwater and marine fungi 