The lesson is divided into 2 parts. The lecture deals with the role and importance of aquatic micro-organisms in the environment and human life. During the course we will learn about the presence of bacteria visible to the naked eye in the Atlantic bottom sediments, bioluminescence microorganisms, plastic and oil digestion capabilities, as well as blue biotech products. Water microorganisms are an invisible power that often resides in environments inaccessible to others. Today, the last passengers on the Titanic are micro organisms. Under laboratory conditions, participants learn about the division of plankton by composition and size fractions, microscopic observation of Atlantic herring larvae, fry and Antarctic krill.