There are some studies out there that show an increasing amount of time to sunburn when people supplement with omega-3 fatty acids.
I've seen discussion on the topic, it seems like it's a balance issue between omega-6s and omega-3s, so reducing omega-6s and increasing omega-3s may help--never seen a study that specifically reduces omega-6s.
Anecdotally, people in TF have had improvements either by increasing saturated fat, I think the side effect is decreasing polyunsaturated fat (omega-6 is a polyunsaturated fat), or some add coconut oil. There's a thread on that if you Search for it.
I didn't supp omega-3s, and it took a while for me to see a change--I did the more saturated fat, less polyunsaturated route, but I can be out a lot longer than I used to be able to be able to.http://wholehealthsource.blogspot.com/search?q=sunburn
There's discussion here, some studies are linked, and some of the Comments may be of interest.