Viruses hold a special place in the everyday life because a billion of them is brought inside our bodies every day with breathing or eating. In the environment, they have the properties of inorganic molecules, while in an infected host cell, they become alive by taking over the translational machinery. Each millilitre of seawater contains over one million viral particles. In the marine environment, they infect all organisms, from unicellular bacteria to multicellular vertebrates. Part of marine viruses is potential pathogens that can infect commercially important aquaculture species. With the increase of aquacultured marine organisms in a controlled environment, the number of viral pathogens is also increasing, thus causing the illness and eventually a problem in the aquaculture. To prevent the occurrence of viral infections, it is necessary to study viruses, which will useful for future research.