I'm a photographer, and while it almost killed me to do so, I emptied out my sling pack... only took one lens and one body. I moved all my velcro partitions and my sling pack was what we took to the park every day. Without all the extra camera gear (like I said, even though I desperately wanted some of my other equipment, this was a family trip, not a photography trip) we were able to fit the camera, extra clothes for the girl, snacks, wipes, first aid kit, wallets, phones, sun block and bug spray, and a few other items, as well as a big water bottle clipped onto the side where I'd normally have my reflectors hanging. So yeah! Highly recommend just taking a big old professional sling pack. It was the perfect bag for all our daily-needed gear for the parks.