Sawa-i-lau worth a visit?

Anyone been swimming in the limestone caves at Sawailau/Sawa-i-lau? (not sure whether it whould have the hyphens - seen it spelled both ways) Would you recommend making a special trip to see them? It's looks amazing, but...

We have only 4 nights/4 1/2 days to spend in Fiji and wondering whether it's worth spending the extra time on the boat to get out there, or if we're better to stick closer in the Yasawas and Mamanucas. Thinking about combining the Mamanuca and Yasawa Taster trips from Awesome Adventures - anyone done that? Any advice/recommendations?