There is daily ferry service between Lahaina on Maui, and Manele Bay on Lanai, with Expeditions Lanai Ferry. The 9-mile crossing costs $60 round-trip and takes about 45 minutes or so, depending on ocean conditions (which can make this trip a rough one).
There is no longer ferry service to Molokai
Expeditions Lanai Ferry. 800/695–2624; www.go-lanai.com.