Crawl off the beach towel and there are opportunities on many Pacific islands for particular, and often unique, adventure activities.

Here's our pick of the adventures in paradise.

CROSS-ISLAND TREK – COOK ISLANDS

For 30 years Pa Teuruaa has been guiding hikers across Rarotonga's imposing mountain interior. Often walking barefoot and in a loincloth, the dreadlocked septuagenarian has traversed the island on foot more than 4000 times, leading visitors into the rugged heart behind Rarotonga's ring of beaches.

Pa's Cross-Island Trek ascends 400 metres from one side of Rarotonga to the serrated ridge that forms the spine of the island. The climb begins among trackside crops – the likes of watercress and taro – but moves quickly into the cloud forest that smothers Rarotonga's interior. It's a steep climb at times, but it's not long.

Atop the ridge, the trail passes beneath the Needle, one of the island's most striking rock formations and an ancient place of worship – look at one side of the towering rock and you'll notice that it's been carved into the face of a god.

Far below you can see out over Rarotonga's airport to lines of waves smashing onto the island's reef.

A natural healer when he's not on the trail, Pa is one of Rarotonga's true characters. He walks silently – he only talks to God when he walks, he tells hikers – but at the regular stops he's effusive with stories. He's led the Dalai Lama across the island, and once guided a woman across on her 96th birthday – they planted a coconut palm on the ridge to celebrate the occasion.

The Cross-Island Trek takes about three hours.

Cross-island trek: Air New Zealand flies to Rarotonga from Sydney, via Auckland, from Thursday to Sunday with  direct flight on Saturday.  The trek can be booked through all Rarotonga hotels See pastreks.com

KAYAKING THE YASAWA ISLANDS – FIJI

The Yasawa Islands stretch like a wind-blown ponytail off the north-western edge of Viti Levu, Fiji's main island. Isolated and basic – the islands have no roads or shops – the group consists of about 20 islands. They're a string of ancient volcanoes rearing out of the Pacific Ocean, with sharp-tipped skylines that drape hundreds of metres into gorgeous white-sand beaches and craggy cliffs. For kayakers, they present a perfect line of stepping stones through the ocean.

Week-long kayak trips tend to focus on the group's northern islands, beginning on Tavewa Island, home to the Blue Lagoon of Brooke Shields and movie fame. From here, with the kayaks filled with everything you need for the next week, it's an island hop, circling out past islands to the north before returning to Tavewa.

You'll stay in small traditional villages, where you can expect heartfelt welcomes, and camp on uninhabited islands for a true castaway Robinson Crusoe experience. On the aqua-perfect water, roll overboard to snorkel among reefs, or simply wait for the turtles and possibly dolphins to surface around you.

Distances between islands are never huge – the widest gap is about 10 kilometres – and trips stick as much as possible to the protected western shores for shelter from the prevailing winds.

Fiji Airways has regular direct flights from Sydney and Melbourne to  to Nadi, where the Southern Sea Ventures trips depart for the Yasawa Islands. See southernseaventures.com

SWIM WITH HUMPBACK WHALES – TONGA

The warm waters of Tonga's Vava'u island group aren't just loved by tropical sun seekers. Every year from around July to November they're also a nursery for the humpback whales that migrate from Antarctic waters to give birth.

For the town of Neiafu particularly, it's become a tourist boon, creating an industry that's put Tonga on the wildlife-experience map (and inspired the recent creation of a swim-with-humpbacks experience on Queensland's Sunshine Coast). A number of boats run trips out to the whales from Neiafu, where guests plunge into the sea in fins and snorkels to witness an amazing ocean spectacle – one of the world's largest creatures in its natural environment.

It's like traditional whale watching, but as if seen from the wings of the stage. Instead of seeing just flukes and breaches, you'll observe mothers and calves gliding through the ocean, gracefully interacting.

Regulations keep a tight control on the encounters  - trips can be done only with licensed whale-watching operators and only four snorkellers are allowed in the water at a time.

Virgin Australia flies twice a week direct from Sydney to Nuku'alofa.  For whale-watching operators, see tongaholiday.com

LAND DIVING – VANUATU

Your holiday adventure urge may not stretch to bungee jumping, but on the Vanuatu island of Pentecost you can at least trace its origins through a spectacular ritual.

Naghol, or land diving, is a traditional harvest ceremony believed to fertilise the land for the annual yam crop. Male villagers scale a wooden tower up to 40 metres high, where two liana vines are tied around their ankles. They then leap from the tower, with the vines pulling them up millimetres before they smash headfirst into the earth. It's a ceremony that was once witnessed by AJ Hackett, who transformed the concept into bungee jumping.

Naghol diving ceremonies take place on Saturdays from April to June, when the first yam crops begin to sprout. There are dedicated land-diving tours, or you can join day trips from Port Vila to Pentecost - these usually book out quickly. If travelling independently you should also book early, as the number of guesthouses on Pentecost is limited.

Air Vanuatu flies six times a week direct from Sydney to Port Vila, and also connects Port Vila to Lonorore on Pentecost Island. For local tour operators, see vanuatu.travel.

CAVING ON ATIU – COOK ISLANDS

About 200 kilometres across the ocean from Rarotonga, the island of Atiu, with a population of less than 600 people, is ringed by limestone – known locally as makatea – that was once a coral reef. Eroded into the limestone is a series of caves, providing the few visitors to the island with the rare opportunity to explore the subterranean world of a Pacific island.

There are at least six cave systems through the ancient coral, including the Tiroto Tunnel, which connects a lake to the sea, but guided tours generally focus on the Anatakitaki Caves and the Rima Rau burial cave.

The Anatakitaki Caves are home to the small and endemic Kopeka, a bird that uses bat-like echolocation clicks to navigate through the darkness. Tours here often end with a candlelit swim inside the cave.

More adventurous are the spelunking trips into Rima Rau, one of Atiu's so-called burial caves. Tunnels here are narrower and require some squirming before you reach a chamber containing the bones of up to 50 island ancestors.

Air Rarotonga flies between Rarotonga and Atiu. Atiu Tours runs trips into the Anatakitaki Caves and Rima Rau. See atiutoursaccommodation.com/tours

SWIM IN THE TO SUA OCEAN TRENCH – SAMOA

One of the most classically beautiful spots in the Pacific, the To Sua Ocean Trench is a sinkhole near Lotofaga village on the south-east coast of Upolu island. Its aqua waters look as though they drilled into the lush garden surrounds, and ferns hang from the rim of the cliffs.

The most challenging moment of a visit to this postcard-perfect swim hole is in descending the steep wooden ladder into the trench. The water below is up to 30 metres deep, so many swimmers take the plunge before reaching the pontoon at the base of the ladder.

The ocean trench is connected to the ocean, about 400 metres away, by a small series of tunnels and chambers. Braver visitors often swim through the tunnel to the sea.

Try to visit at low tide and during times of gentle seas, when currents and wave action aren't so tumultuous. samoa.travel/sightseeing/x40/to-sua-ocean-trench

Virgin Australia flies three times a week direct from Sydney to Apia. Lotofaga is about a one-hour drive from Apia.

FIVE OTHER GREAT PACIFIC ADVENTURES

GR1 (New Caledonia): Mimicking the French system of grande randonnee hiking trails, the GR1 is a five to six-day hike that runs through New Caledonia's interior behind Noumea. See office-tourisme.nc

White-water rafting (Fiji): Splash through the Upper Navua Gorge on Viti Levu, with its narrow chasm and string of grade II to III rapids. See riversfiji.com

Vaka sailing (Cook Islands): Sail overnight between Rarotonga and Aitutaki on a traditional Cook Islands vaka (canoe), using only the stars and swell for navigation.

Diving at Rangiroa (French Polynesia): Head below the ocean surface at Tiputa Pass, where tides flow in and out of Rangiroa's spectacular lagoon, bringing with them a traffic jam of manta rays, dolphins and hammerhead sharks. See topdive.com

Surf at Teahupoo (French Polynesia): It's been called the "heaviest wave in the world" so you may prefer just to sit and watch this legendary reef break on Tahiti's south coast.