On a recent trip to Efate, my family visited the Turtles at Crystal Blue Lagoon. It's not listed as an Attraction on TripAdvisor, so I thought I'd leave some information here to assist future visitors.
Come at high-tide to swim with the turtles. The children will love it! Don't bother with the accommodation.
Also, please note that this is NOT the Blue Lagoon swimming hole that you'll find on the East coast of Efate. Nor is it the Bluewater Island Resort that is nearby.
Crystal Blue Lagoon is a marine conservation area that collects turtle hatchlings and raises them until they're a few months old and releases them to the wild. When you visit, you'll get to see the young turtles and you're welcome to pick them up and have a play with them. Actually, our pre-teen children thought this was the highlight of their whole Vanuatu trip!
Even better is an enclosed rock pool containing various turtles (one aged 60 years!), reef sharks (they're safe), fish and a sting-ray (that has had its barb removed). We were told that, if you come at high tide, you get to swim with them. Unfortunately we didn't know this, so we missed the opportunity, but we still had the opportunity to feed pawpaw to some of the turtles.
There's a nearby beach that looks great for snorkeling but the weather was a bit harsh during our visit so we didn't swim. There is also accommodation and conference facilities, but frankly they looked pretty basic so I'd recommend just planning a day visit.
While we were there (July 2011) there was construction going on. Apparently Crystal Blue Lagoon was previously in a different location and was sold to a different operator. It then fell into disrepair and the original operator started again in this new location. It's owned by a Vietnamese gentleman and is run in cooperation with the Vanuatu Fisheries Department. The staff even live in their own on-site village.
There is accommodation available, but it didn't look like particularly high quality. I'd suggest coming for the turtles, but not staying overnight unless you're a marine biologist.
Crystal Blue Lagoon is a good 30-minute drive south-east of Port Vila along some unsealed roads (in the neighbourhood of Tamaru on the Sands) so you'll either need your own rental car or take a bus. We negotiated with a bus to take us there, wait for a couple of hours, then drive us back for VT 5000 (Approx AUD$50). You might be able to bargain for a better deal. We recommend that you take the shorter and far better, partially sealed White Sands road to drive to Crystal Blue Lagoon, unless you want a really bumpy and much longer unsealed road experience!
Entry cost VT 1500 per adult and VT 500 per children (so a family of four cost us VT 4000 / AUD $40).