Greece is a choose-your-own-adventure water trip: volcanic cliffs in the Aegean, calm cave coasts in the Ionian, and long-season warmth around Crete. Most itineraries blend short boat rides and easy shore entries with visibility often around 15 m to 30 m. Summer is peak for water time (often 24°C to 28°C), but the Aegean's Meltemi winds can steer you toward leeward sites or different regions. Late spring and early autumn usually trade slightly cooler water (roughly 18°C to 24°C) for fewer crowds and smoother travel days. Add strict protections for turtles, monk seals, and underwater antiquities, and Greece rewards divers who plan with local operators and respect access rules. Use Athens as the main gateway, then commit to one region such as Santorini or Crete.