There’s no boat or ferry yet between Kampot and Phu Quoc. (Koh Tral in Khmer.)
We will let you know when one is planned. Promise!
But you can get there by land in half a day from Kampot or Kep.
Kep is half an hour quicker.
Just call this number (or message) on WhatsApp or Telegram. They’ll get you door to Island service from Kampot or Kep. (or Island to door service if coming from Phu Quoc to Kampot or Kep.)
+84 949 192 616
or check out the website.
(look under “Bus Service”, but they have nice vans from Kampot and Kep, everyday.)
While going directly by air or sea to Phu Quoc, you need only a passport, (no visa), many countries will require a visa in advance to get to Phu Quoc by land.