I have visited Rarotonga quite frequently and the usual beach habitat is quite rocky, I would guess the island of Samoa would be very similar. However, this doesn't mean fishing from the shore cannot be very successful. If you can cast a fly (or plastic) then there are plenty of fish who will oblige, a lot of the larger fish are predators. Also you could consider fishing with a medium sized plastic float with the bait suspended just off the bottom. The float with a small lead bullet will cast quite a long way on a surf rod.
May I give you one little tip. Should you get among the fish, the local people will think the world of you if instead of releasing the fish, you give them away. Your 'mana' will be at the top of their list, and your generosity may be returned ten fold. Generally Island people, by New Zealand standards, are quite poor. By making a gift of food you will be treated as someone truly special.