Oomycetes, also known as water molds, are a group of fungus-like organisms that belong to the kingdom Stramenopila. They thrive in aquatic environments and damp soil, playing essential roles in ecosystems as decomposers. Oomycetes reproduce both sexually and asexually, producing spores that can spread easily in water. Some well-known oomycetes include Phytophthora infestans, the pathogen responsible for the Irish Potato Famine, and Saprolegnia, which affects fish and other aquatic organisms. Unlike true fungi, oomycetes have cell walls made of cellulose rather than chitin, which distinguishes them from traditional fungi.