Sawa-i-Lau is one of the most striking natural landmarks in the Yasawas — a domed limestone cavern rising directly from the sea on the island of the same name near the northern end of the chain. The main chamber is a tall, oval space with a pool at its base, lit by a circular opening in the ceiling that sends a column of blue-green light down into the clear water. You swim to enter and swim around inside.
The setting is genuinely otherworldly. The water inside is calm, slightly brackish, and lit from above and from the underwater cave mouth that leads from the ocean. Local boatmen bring visitors here as part of day trips from nearby resorts, and village guides collect a small fee. There is also a second chamber, reached by ducking under a submerged passage — this one is darker and requires a guide with a torch, but it is worth the brief submersion.
Most resorts in the northern Yasawas include Sawa-i-Lau as a day-trip destination. If you are on a budget resort further south, ask the Yasawa Flyer crew whether the boat stops here on its regular run — some operators allow passengers to disembark for a couple of hours and reboard a later service.