The mesh netting or lining of these shorts protects your most sensitive parts from getting chafed or rubbed the wrong way. Like swimsuits, swim shorts for women use a special material to keep you protected. Since swim shorts often have a looser fit (which means more potential for rubbing and chaffing) it's a no-brainer for quality swimwear (like T9!) to include mesh lining, netting or built-in briefs in their swim bottoms.