The phylum Blastocladiomycota, commonly called the blastocladiomycetes or blastoclade fungi, is a small group of aquatic fungi characterized by their production of motile zoospores with a single posterior flagellum. These fungi typically grow on decaying plant material, algae, and sometimes in soil, playing a role in decomposition and nutrient cycling. Some species, such as Allomyces, are well known as model organisms for studying fungal life cycles due to their alternation of haploid and diploid generations. While generally saprophytic, certain blastoclade fungi can also act as parasites on plants, algae, or small invertebrates, making them ecologically diverse despite their limited number of species.