Kip at the Kalua’a Hotel will eventually install a navigation app on your Pi Phone so you can sail between islands.
A key item needed for progress is a Joke Book , which you can find in a bush near the ruins outside. Leisure Suit Larry - Wet Dreams Dry Twice Pobie...
If you are stuck on a for Nari or Pobie, please let me know: What items do you currently have in your inventory? Which island are you currently on? What was the last thing Nari asked you to do? Kip at the Kalua’a Hotel will eventually install