Yonaguni

Before departure: provide certification and recent log, discuss current drift competency, fitness and medication, and ask about the specific skipper's weather cancellation threshold. YDS describes mid-water descent without mooring lines, guide-only course changes, a no-stop plan, SMB-assisted separation procedures and boat pickup. Never pursue hammerheads, split from the group to photograph them or chase downcurrent; train with the SMB before diving. Divers must stay out of caves or penetrations lacking continuous direct ascent unless appropriately trained and equipped. YDS safety rules.

After diving: DAN suggests at least 12 hours after a single no-decompression dive and 18 hours after multiple dives/day or consecutive days; 24 hours or longer after required decompression is a more cautious minimum. These are not guarantees, and many travelers schedule a full nondiving final day. Report suspected decompression symptoms urgently, do not fly, and activate emergency services. DAN guidance.

Snorkeling and shore safety: the tourism association explicitly prohibits swimming at Rokujo and Ubudumai beaches and says other beaches lack lifeguards, while regional authorities warn of rip currents, jellyfish and downcurrents. Independently snorkeling from picturesque shorelines is not a validated substitute for a guided trip. Town notice; Regional safety.

Yonaguni Town Clinic is the principal local facility identified in this research, at Yonaguni 125-1, tel. +81-980-87-2250. The clinic posts routine appointments on weekdays, no regular care at nights/weekends/holidays, and specifically instructs emergencies to call 119. A locally available hyperbaric recompression chamber was not verified. Do not promise a particular evacuation endpoint or transfer time: rescue and onward treatment depend on assessment, weather and available transport. Bring medications and dive insurance that covers emergency rescue, possible air transport and recompression; ask the operator for its current emergency action plan. Clinic; DAN.

The local dive provider tells divers not to chase hammerheads, and Okinawa tourism guidance asks snorkelers not to stand on coral, divers to avoid coral contact and visitors not to feed marine life. Okinawa Prefecture publishes restrictions against harvesting protected reef organisms, corals, sea turtles and reef substrate. Do not collect artifacts, carve rock or touch the Monument; no special claim of legal archaeological protection is made without a direct ruling. Respect cultural and private pasture access restrictions, follow boat captains on anchoring, and carry all rubbish out. Wildlife etiquette; Coral stewardship; Okinawa rules; Local access restrictions.