Several tour operators on Phu Quoc offer the chance to get off the island and into the sparkling turquoise water that surrounds it.The most popular option is a full day of either snorkelling or diving -- expect to pay around $17 for snorkelling, $30 and up for diving.
Other tours will take you on a circle around the island to a few off-the-track beaches, to the deserted islands to the south, or on a night time squid hunt.
The last option seems to be particularly popular -- once you've caught a squid, the onboard chefs will prepare it in several different ways.
Most guesthouses have brochures from a few different companies, and can arrange the tours for you.