The marine environment is subjected to several factors that affect the metabolic development of all organisms, one of which is the introduction of heavy metals into the aquatic ecosystem. Regular biomonitoring of heavy metals in the marine environment has become a significant concern. Using bioindicators that include plants, animals, and microbes is highly recommended, as they spontaneously reflect the quality of the marine environment. Due to their significant ability to accumulate elements and reflect the elemental content in the aquatic environment, marine macrophytes as bioindicators are widely used. They also exhibit both spatial and temporal evaluations of contamination due to their biosorption abilities as metals adhere to their cell walls, offering a passive and sustainable approach to monitoring pollutants. Also, seagrass, molluscs, turtles, fish, and sponges are widely used as bioindicators to indicate heavy metal content in the marine ecosystem. Due to their long lifespan and high sensitivity toward environmental changes, corals can provide a record of historical pollution levels in marine ecosystems. This chapter provides a comprehensive analysis of the capability of macrophytes, algae, and corals in the field of biomonitoring. It elucidates the processes involved in the assimilation, accumulation, and detoxification of pollutants while exploring their utility in short-term, medium-term, and long-term assessment strategies. By incorporating species such as Pontederia crassipes (Mart.) Solms, Ulva L., and various corals, biomonitoring initiatives can effectively tackle a wide array of environmental issues, thereby enhancing the sustainable management and rehabilitation of aquatic ecosystems.