Rottnest Island: Limestone Reefs and Quokkas, 30 Minutes From Fremantle

Perth divers have it good. Thirty minutes on a ferry from Fremantle and you are standing on an island that is basically a drowned dune ridge, ringed with limestone reef, caves and bays that drop away from the sand.

That is Rottnest Island. Or Rotto, as everyone in Western Australia calls it. Nineteen square kilometres, 18 kilometres offshore, no cars, and around 300 people living there full time.

The reason it is worth your attention is the geology. Rottnest sits on a base of aeolianite limestone, and limestone does interesting things underwater: ledges, swim-throughs, caves. Wikivoyage calls it the best snorkelling in the Perth metropolitan area, and the same reefs and caves are what divers come for.

What the diving is really about

This is reef diving, not wreck-hunting-at-depth diving. The bays and beaches are the attraction, and they come with reefs and caves that you can work your way around.

The island is low and sandy, sparsely covered in scrub, with big salt lakes at the eastern end that turn pink. Underwater, the story is that limestone base: the same rock that built the island's colonial cottages was quarried here, and the same rock forms the reef structure offshore.

Volkersen, who anchored a Dutch ship here in 1658, warned that the island was dangerous to approach because of rocky reefs level with the water and below the surface, almost the whole length of the shore. Bad news for a seventeenth-century navigator. Good news for you.

Getting around a car-free island

There are no cars on Rottnest. You cycle, or you take the Bayseeker bus, which generally runs between 8:30AM and 3:30PM with a day ticket that lets you hop off wherever you like.

Bike hire runs around $30 a day, from the ferry terminal in Thomson Bay or through the ferry company. A full loop of the island is about 25 km.

Rough cycling times from the Settlement at Thomson Bay, from the Wikivoyage guide:

• The Basin – 5 minutes
• Geordie Bay – 10 minutes
• Wadjemup Lighthouse – 20 minutes
• West End / Cape Vlamingh – 50 minutes to an hour, depending on the wind

One tip worth stealing from the guide: ride a full loop in the morning, then decide which bay you actually want to spend the day at. And the further you go from the Settlement, the fewer people you share the water with.

Sea temperature through the year

The water runs warmest from January through April and coolest around September. Wave heights offshore are lowest in the late summer and spring months and build through the middle of the year. The island's climate is much the same as Perth's, though a touch cooler for being further south and surrounded by ocean.

One date to note: school leavers take over the island for a week towards the end of November. Accommodation is hard to come by then, and the crowd is a party crowd.

What lives here

Rottnest is an A-class reserve, the highest level of protection Western Australia gives to public land. That matters for what you see.

There are colonies of Australian sea lions and southern fur seals around the island. Above water, quokkas are everywhere, and they are the reason the island has its name at all: Willem de Vlamingh spent six days here from 29 December 1696 and called it 't Eylandt 't Rottenest, Rats' Nest Island, after mistaking them for oversized rats. He also described the place as pleasurable above all islands he had ever seen.

Plenty of birds too, and three native tree species, the Rottnest Island pine being the one you will notice.

Wadjemup: the island's other history

The Noongar name for the island is Wadjemup, meaning 'place across the water where the spirits are'. People were here at least 17,000 years ago, when Rottnest was a hill on a coastal plain; rising seas cut it off around 6,500 to 7,000 years ago.

From 1838 to 1931 the island was used as a prison and forced labour camp for more than 3,600 Aboriginal people, held in extremely harsh conditions. At least 373 died and were buried in unmarked graves north of the Quod. It is the largest known deaths-in-custody grave site in Australia, now the Wadjemup Aboriginal Burial Ground.

Most of the historic Settlement you walk through between dives, including the church, the Salt Store and the waterfront cottages, was built by that forced labour. Worth knowing before you arrive, as the Wikipedia article lays out in detail.

Planning it

Ferries run daily from Perth. From Fremantle the crossing is 30 minutes; from Barrack Street Jetty in Perth it takes longer, and there is also a service from Hillarys Boat Harbour. Fares start from $29, and landing fees are included in the ferry price.

Rottnest Express makes the crossing five to six times a day. In summer, SeaLink and Rottnest Ferries leave Fremantle roughly hourly with staggered departures, so in practice there is usually something going every half hour.

Around 780,000 people visit each year, and peak periods can put up to 15,000 on the island at once. Book accommodation early if you want to stay rather than day-trip.

Heading to Rotto? Log your dives in Scubaspot with the bay name attached, so the next diver can tell The Basin from Geordie Bay before they hire a bike. Add your cave and ledge shots, rate the reefs you dive, and if a sea lion comes to look you over, that photo belongs in the feed.