I'm thinking of giving it a try. I found this article here by someone in Hawaii who does it and says all the surfers there do. Here's her post:

I live in Hawaii, so one does get sticky, icky, irritated, and sunburned quite easily. Especially if you're prone to it like I am. I have gotten the worst rashes in my underarms and sometimes around the "area" because of the environment. I apply diaper rash cream after my nightly shower to these areas and it helps to keep the irritation down.

I also use diaper rash cream as part of my homemade sunscreen. Many of the surfer's here make their own sunscreen and I decided to make up my own recipe. It consists of:
1/4 cup Diaper Rash Cream
1 tbsp Coconut Oil
1 tbsp Cocoa Butter
1 tbsp Aloe Vera Gel
1 tsp Sesame Oil
1 tsp Beeswax
I put them all in a ceramic bowl that's set in some boiling water and melt all the ingredients together. I like a shine on my skin at the beach and this gives me that "glow" even though it fades a bit half an hour after applying. I've never gotten burned using this and I like it because it's all physical block instead of chemical since I'm allergic to most chemical sunscreens. It's not waterproof in the typical sense. But the beeswax makes it more water resistance. You should be reapplying any sunscreen every 3-4 hours anyways, so reapply after a swim wasn't a bit deal for me.
More here: http://www.makeupalley.com/product/s...p?itemid=73527