Dr. Giorgos Chatzigeorgiou and Ioannis Rallis from the Institute of Marine Biology, Biotechnology and Aquaculture, at the Hellenic Centre for Marine Research in Crete, are scientific divers who investigate 'Non-indigenous and Invasive Species in Ports and Marinas', despite the challenges of poor visibility, ropes, chains and unpredictable marine traffic.  Their research shows a surprisingly high species richness in these extreme environments, but also a high number of non-indigenous species, mostly introduced to the Mediterranean Sea via the Suez Canal, attached to ships' hulls or transported and discharged in ballast waters. Human disturbances lead to great fluctuations in salinity, turbidity, dissolved oxygen and high rates of pollution, allowing opportunistic alien species to succeed because of their ability to adapt to these pressures and environmental changes.  Combining direct observation, sampling and conducting experiments underwater, their work identifies and tracks the impact of introduced species on these environments. Analysing data in LifeWatch ERIC facilities, they are developing standardised protocols for the study of biodiversity in these areas, that can be widely applied on a regular basis to get rapid results. Preventive measures in biofouling management and increasing public awareness of the impacts of non-indigenous species on marine ecosystems will help develop effective management strategies.