If you’re going to Perth and have at least 24 hours free, you owe it to yourself to visit Rottnest Island — it’s gorgeous, accessible and has quokkas, for the love of god.
Getting to “Rotto” is easy — If you’re staying in Fremantle (“Freo”) you can catch a ferry with either Rottnest Express (from the B-Shed location near the Fremantle train station (multiple departures from 7.15am to 3.15pm, arriving Rottnest between 8.00am and 4pm, taking about 45 minutes), or from Northport if you’re driving) or Rottnest Fast Ferries from Hilarys Boat Harbour (multiple departures 7.30am to 5pm) a bit north of the city. If you’re stationed in Perth, Rottnest Express also runs ferries down the Swan River from Barrack St in the city., leaving at 8.30am and arriving Rottnest at 10.45am (which stops at both B-Shed and Northport along the way). In any case, it’s not a long trip, and especially from Perth there’s some interesting scenery along the way.
An adult fare on Rottnest Express from Perth is around $100 AUD (including the Rottnest Island access fee) or $80 from Fremantle. Prices are comparable on Rottnest Fast Ferries, so it’s more a question of where you’d like to depart from (I’d personally recommend Rottnest Express’s locations) than anything.
Once you get to the island, you’ll head to the visitor centre at the head of the main jetty to check in. You’ll want to have reserved accommodation already. A campsite currently runs $36 (a bit less, admittedly, when I visited recently, but in any case the cheapest lodging on the island), whereas a single/family room at the Rottnest Hotel runs $51/$111, and bungalows/dormitories/etc can run anywhere from $70 a night in low season to $220 a night in high season. More than anything, just realise that there’s a lot of options to suit a lot of budgets and group sizes, and so long as you’re planning ahead there’s probably something available to suit. For meals there’s a decently-stocked supermarket and BBQ for self-catering, as well as full-price meals at the Rottnest Hotel and cheapier stuff in the main settlement at the Rottnest Bakery and nearby Subway. There’s a Bankwest ATM if you run out of cash, and the supermarket also has your various sunscreen/souvenir/beachy items covered.
You can rent bikes as well as masks/snorkels/flippers from Pedal and Flipper in the main settlement for $30 for 24 hours // $21 for 24 hours respectively, though don’t expect anything other than barebones quality. The ferry companies will also rent you the same equipment for similar (if ever so slightly higher) prices, which you can reserve then you make your ferry booking if you’re so inclined. Pedal and Flipper also rents everything from basketballs to cricket sets to surfboards, so if you’ve got a debit card you’re pretty much covered for recreation.
As for what to do when you’re there, I’d certainly recommend renting a bicycle. There are buses that ply the routes around the island (there’s no other private motorised transport allowed, thankfully), but if you’re physically able bicycle is definitely the way to go. Snorkelling, likewise, is a treat. Little Salmon Bay and The Basin are two of the finest spots, and are sheltered enough for children, though Parkeeet Bay and Little Armstrong Bay off the north coast as well as Parker Point and the east edge of Salmon Bay on the south coast are also good choices. There are wrecks to SCUBA dive as well at various points around the island (historically treacherous rocks!) if you’re keen.
As for tours, one-offs like the Oliver Hill tunnels and Wadjemup Lighthouse run about $10 AUD a pop, and you can purchase one-day “island explorer” passes for around $20.
Whatever way you choose to visit Rottnest, however, you owe it to yourself to just GO. Popular though Australia is with international (and specially anglophone) tourists, the west coast gets precious few visitors compared to the Cairns-to-Sydney-to-Melbourne circuit in the east. More’s the pity- Rottnest is a true highlight of Australia, and a unique and wonderful bit of the little-visited southern Indian Ocean. And that’s BEFORE you add in the quokkas.