South Florida Clean Coastal Waters Act of 2018 This bill addresses harmful algal blooms and hypoxia in the South Florida ecosystem. An algal bloom is a rapid growth of algae that may create toxic or hypoxic (severely low-oxygen) conditions that are harmful to humans, animals, aquatic ecosystems, and the economy. The Inter-Agency Task Force on Harmful Algal Blooms and Hypoxia must assess potential approaches to reduce harmful algal blooms and hypoxia in the ecosystem. The task force must also submit a plan, based on the assessment, for reducing, mitigating, and controlling harmful algal blooms and hypoxia in the region.