Understanding how higher fungi with their spectrum of cellulolytic and ligninolytic enzymes degrade wood tissue, while labyrinthuloids and thraustochytrids further contribute to the dissolved organic matter entering the open ocean is essential to marine ecology. This work provides an overview of marine fungi including morphology and ultrastructure, phylogeny and biogeography. Biotechnology is also turning to these organisms to develop new bioactive compounds and to address problems such as decomposition of materials in the ocean and bioremediation of oil spills.