Mesh dive bags are popular for a number of reasons. First, they're super lightweight and that's always a good thing. Second, the loose-weave mesh material makes it easy to see what's inside, a big plus when digging around for particular gear items. Third, they're water draining, so when the day's diving is over, you won't have to carry half the ocean home with you in a pile of water-soaked gear. And fourth, the mesh weave allows for lots of air circulation which helps eliminate odors and control mildew when storing gear between dive trips.