Nothing much at a working port and a small town with 2 casino!!! The swimming beaches are located on other parts of island. Cruise does organise excursions which can be booked on board but I consider them fairly expensive and not very interesting. I prefer checking out the fantastic French bakeries and restaurants for lunch. Very reasonable pricing compared to similar restaurants in Melbourne/Sydney.
Lifao Island is predominantly scuba or snorkeling. Good shallow coral reef fish in fairly shallow waters on left of jetty. Need to be aware of sharp corals.
Do not miss the cheapest freshly cooked cray fish on Mystery Island. At A$50 for a huge at least 2.5kg cray. Will likely cost $120 or more for that in Melbourne/Sydney restaurants.
Isle of Pines has a snorkeling place call "The Aquarium" about 15 mins by taxi away from the jetty at Oro Bay. Well worth the visit as it is a sheltered lagoon protected by coral reef and hence no currents but the diversity of the fish at this place is incredible.