What to do in Fiji - Ecotours

The Oceanic Society, an award-winning organization, has natural history and ecotourism expeditions to Fiji. A marine naturalist accompanies its annual 11-day snorkeling to the colorful, pristine reefs off Namena and Taveuni islands in northern Fiji. The trip includes village visits and bird-watching excursions.
Seacology, an organization dedicated to preserving island cultures and environments, has an annual trip to Jean-Michel Cousteau Fiji Islands Resort and occasionally to Samoa.
Fiji Adventures offers several packages, one of which combines several cultural activities offered in Fiji such as river rafting, cave and waterfall visits, and a trip into Viti Levu's interior. The packages do not include airfare, but they save you from having to arrange each activity after you arrive in Fiji.
The environmentally and culturally friendly Active Fiji uses a 42m sailing schooner to explore out-of-the-way islands in northern Fiji. The boat goes to Fijian villages and carries mountain bikes as well snorkeling and diving gear.
The nonprofit Greenforce sends expeditions to help survey Fiji's coral reefs for the World Conservation Society. They'll even teach you to dive while you're there. The trips last from 6 to 10 weeks.