Just planning our trip to Rottnest which is just a 1 day over and back from Fremantle. The plan is to take the 9:30 ferry across and the 4:25 ferry back to Fremantle. As we do not want to go if the weather is bad we would like to book/buy tickets on the day but worried that it may book out if we do not pre book. Any comments on the likely hood that it will be booked out? We are in Fremantle for 6 days so are flexible (somewhat) to going on a different day. We are there near the end of August and the original plan is to go to the island on a Monday.