Here's what other sites are saying:
Eye-up your line and start cranking with the Immersion Research Thin Skin Rash Guard under your PFD. This tight-fitting rash guard keeps the sun off your back while you hike up river and then work your favorite stretch of rapids. Flat seam construction means it won?t chafe under your PFD, and the high neck offers some protection from sunburn.
- Backcountry.com refers to the men's version