Plan conservatively. Use local guides for caverns, wrecks, offshore walls, and archaeological routes. Carry a DSMB, whistle, computer, and adequate exposure protection. Do not rely on calm skies as proof of calm seas: Aegean northerlies can build chop quickly. Avoid alcohol-heavy nightlife before early dives, and build no-fly time after repetitive diving or deeper profiles. Freedivers should never train alone, should use a buoy and line safety, and should not combine aggressive breath-hold sessions with scuba profiles without conservative professional guidance.

Call 112 or 166 for urgent medical help and 108 for marine emergencies. For suspected decompression illness, stop diving, administer oxygen if trained and available, hydrate only if conscious and safe, keep the diver lying comfortably, and contact emergency services and DAN Europe. Hyperbaric and diving-medicine support is concentrated around larger centers such as Athens and selected regional facilities, so remote islands may require transfer. Carry insurance that explicitly covers scuba, freediving where relevant, evacuation, and recompression treatment.

Use a no-touch, no-take, no-chase rule everywhere. Do not anchor in Posidonia seagrass. Do not enter monk-seal caves. In Zakynthos, keep distance from turtles, avoid lights on nesting beaches, and follow park zones. In Alonissos and other protected areas, respect access limits. Underwater antiquities belong to the state and are protected: photograph only, never move or collect. Choose operators that brief wildlife behavior and site rules before selling an encounter.