This chapter is a part of the book “Recent advances in biometrics” introduces the importance of biometrics in the aquatic studies in brief view. Biometric measurements (Morphometric, meristics and description) are widely used in various fields’ “taxonomy, species identifications, monitoring of pollution, species abnormalities, comparison, environmental changes, growth variation, feeding behavior, ecological strategies, stock management, and water quality of aquaculture. These data were collected from several articles and books of aquatic animals and presented both applications and required considerations for biometric implementations. It is important also to detect sexual dimorphism, adaptations during evolutionary time and diminishing intraspecific competition by increasing niche portioning. The biometrics could be applied for various aquatic organisms as dolphins, sharks, rays, mollusca, crustaceans, protozoa, … etc. and for specific organs like teeth, otolith and appendages by different techniques and preservations. Scientists are still applying these measurements even with the presence of advanced techniques like PCR as they are low in cost, faster and more applicable. This chapter also presented some recent trends including animal’s biometric recognition systems, followed by challenges and considerations for the biometrics implementations. It is recommended to apply biometrics in wide range together with modern techniques considering the specificity of its quality and preservation status.