Grotte Bleue

**Tour vs DIY:** Guided tours dominate the Blue Cave (20+ operators), providing boat transport, equipment, safety guidance, and underwater photography (usually included). DIY shore entry is possible but requires strong swimming (200-meter swim to cave, currents can be tricky), equipment rental from Maeda dive shops, and confidence in open water. First-timers: book a tour. Experienced snorkelers: DIY saves ¥3,000 and avoids crowds. **Avoiding crowds:** The Blue Cave sees 100+ visitors daily in peak season (July–August), with 5–10 groups inside simultaneously. Early morning tours (first departure 8:00) encounter fewer groups. Alternatively, visit off-season (November–March) when water temperature drops to 22°C (wetsuit required) but the cave is nearly private. The blue glow intensity is identical year-round. **Visibility factors:** The blue glow requires three conditions: (1) sunlight (overcast days mute the effect significantly), (2) calm water (waves stir up sediment reducing clarity), and (3) midday sun angle (optimal 11:00–14:00). Check weather forecast and sea conditions before booking — operators cancel trips in bad conditions but only refund if they cancel, not if you cancel due to weather.