The wrong harbour
Toyapakeh, Banjar Nyuh and Buyuk are all "Nusa Penida". Landing at the wrong one puts you an hour from your driver.

Transfers
Thirty minutes on a ticket, or an hour on your own hull. Most people need the ticket, and this page says so.
A "Nusa Penida" ticket lands at three different harbours. Match your landing point to your driver.
Scheduled fast boat from Sanur
Fast boat via Nusa Lembongan
Private speedboat charter
Private yacht or catamaran day
The scheduled boat departs on a fixed timetable from Sanur; the private options depart from Sanur, Serangan or Benoa on yours. If you are two people and just need to get there, the ticket is the right answer.
Practical
None of them are the crossing. All three are avoidable with one check before you book.
Toyapakeh, Banjar Nyuh and Buyuk are all "Nusa Penida". Landing at the wrong one puts you an hour from your driver.
Morning departures cluster. Arrive forty-five minutes before yours, not fifteen — the terminal is organised now, but it is not fast.
The pier walk is exposed. In rain, anything not waterproofed gets wet before it reaches the boat.
Send the date and how many of you there are. If a scheduled ticket is the sensible answer, the desk will tell you that.