Atata island consists of tiny local fishing village and a small tourist resort, Royal Sunset Resort. Unless you have access to your own boat, the only way to get to the island is by the resort ferry. The ferry leaves every morning from the main wharf in Nuku’alofa and returns in the afternoon. The resort is happy to organise day trips or, of course, overnight accommodation.
The cache is a located within thick scrub adjacent to the beach between the resort & the village. You are looking for a camouflaged pill container hidden in a location resistant to be being muggled by the village pigs.
Small note on cache maintenance: There is a local cache guardian. Name and contact info on file with geocaching.com.