All the tour operators push expensive speedboat trips to Phi Phi, but locals just take the regular ferry from Rassada Pier for 450 THB each way. Takes 2 hours instead of 45 minutes but it's way more comfortable and you can bring your own food.

Ferries run at 8:30am, 1:30pm, and 2:30pm daily. Buy tickets at the pier, no need to book ahead unless it's peak season. The boat is big enough that you won't get seasick like on those bouncing speedboats.

Once you're on Phi Phi, you can explore at your own pace instead of being rushed through a tour group schedule.