Locals named it Hawiyat Najm believing a fallen star dug it: the Bimmah sinkhole of mixed turquoise water (fresh meeting sea) — descend its stair and swim a naturally complete pool, parked and prepared on the Sur coastal road. Ninety minutes from Muscat: make it the coast day's first stop (Bimmah → Wadi Shab → Sur); swimming is free with tiny fish giving gentle spa nibbles; morning before the tour buses leaves the pool clear and calm.