Ellison’s Cave, USA
Son Hang Doong, Vietnam
Secret blue cenote in the Ik-Kil park in Mexico. It's open daily to swim, dive, snorkel in the crystal blue water. (And the entry is only $3).
open cave, ahrax mellieha, Mellieha, Malta - and situated in the North of the island. Reachable by canoe/boat from Armier bay from the Malta
Where is this?