Took RCI arranged two hour bus tour of Noumea surrounds and aquarium. Enjoyed the tour. Walked around a bit afterwards and had a French lunch at the town square which was also nice.
The second stop was Lifou, New Caledonia. Snorkeling was very nice. Clear water and a lot of variety of fish. Get there early as the crowds can get bad.
The third stop was Mystery Island in Vanuatu. Snorkeling on the far side of island was only a couple of minutes walk and the best snorkeling of the entire trip. Saw sting rays and many different types of fish.
The last stop was Isle de Pines. Paid a taxi AU$50 to take us both to the "Aquarium" on the far side of the island (and back). The Aquarium lives up to its name. Later we snorkled around a small island across from where we docked and saw Lionfish, an octopus and many different fish. A slight surge here meant that the water was not as clear.
We were disappointed that we could not hire scuba gear at any of the islands (we're both PADI certified). Two had scuba gear for hire but their boats left before our ship even anchored.