I was in French Polynesia for 7 weeks and had no issues with stone fish or cone shells. In fact, I never even saw any of these, except while diving. So no need to bring anything, as there are plenty of sandy beaches where you don't have to be afraid of stepping on either.
Also, I generally don't recommend reef shoes, except for places like Croatia, where you sometimes can't get into the water without climbing across sharp rocks.
Reef shoes tend to give you a feeling of safety and you are more likely to step on fragile coral which you'll most likely destroy by doing so. So please, don't buy any reef shoes and enjoy French Polynesia.
By the way: if you don't know yet where to go, here is a great overview of the 10 different islands we visited during our trip: www.travelintense.com/eco-travel-destinations/french-polynesia
Michaela almost 3 years ago