To celebrate the summer Konami is adding a Swimwear Uniform to Metal Gear Solid V: The Phantom Pain, that can be equipped by FOB staff. You will have to develop the items first, after you’ve obtained them as an Event Points reward. From the official website:
Show off those beach bods! Swimwear uniforms now available for FOB staff
Perfect for summer FOB fun! Your FOB staff can now wear new uniforms – swimwear. In addition to your security guards, you yourself can also dress down when infiltrating enemy FOBs. Look forward to a variety of designs as future Event FOB rewards. Find a stylish look that suits you, and show any and all trespassers there’s no lifeguard at this party!
* Swimwear designs are online development items. Develop them by going to [DEVELOPMENT] after obtaining them as an Event Points reward.
* To have FOB security guards wear swimwear, go to [SECURITY SETTINGS] -> [ADVANCED SETTINGS] and set the use of special gear (swimwear).
* Your soldiers can also wear swimwear when invading an enemy FOB, but neither Snake nor your avatar soldier can wear it.
* To view staff in swimwear, after equipping it, go to [FOB MISSION] -> [TRAINING/VISIT DESTINATION] and select your FOB, then proceed to training or visit.
* Mother Base staff in METAL GEAR SOLID V: THE PHANTOM PAIN (the main game) cannot wear swimwear.
Source: MGSV Official Website