What is there to do in the South Pacific?

Like the southern polynesian islands cook, french poly, kiribatia. What is there to do other than scubadiving.I like scubadiving but is there anything more to do. The pictures look great. It looks way more beautiful than hawaii. But it also looks very isolated and empty. And it probably is, if I look on the map. If you travel by these islands by boat, is there nothing more than resorts ? What activities are there to do. And the nature, is it all flat and small islands. Or are there also bigger islands, jungles, mountains rivers etc ??