I like to use a chafing powder added early on before I start surfing. Normally before I get into the car to go to the beach, I dust a little on for pretty much any activity. I am a hiker too because a lot of the best surfing spot where I'm from require a little hiking to get too. Anyways, This stuff works well whether your in the water or on land as long as your aren't sweating already and the product has completely been absorbed into your skin. don't put this on right before you go into the water. It will wash right off. If you have any type of chafing or skin irritation problem, I recommend you going to this site. http://www.antimonkeybutt.com/
Originally, I used this product for my thigh gap problem because my legs would rub together during surfing and hiking. Now, I just use it as a standard for any activity that requires a lot of moving. I don't trust other products. I used to use Gold Bond afterwards too, but this works better in my opinion.
I hope this can help.