No one knows, including Seaworld, so I'll answer. There are a few places with regular, large and extra large lockers. We used the ones just past Customer Service and to the right in a corner. They use an image to show that regular will hold one backpack, a large 2, and an extra large 3. The dimensions of the extra large seemed to be 22 by 14 by 12. The bottom line was that we put 2 "Sprit Airlines Sized" backpacks in standing up, and one on top and angled down. We stuffed our thin jackets and other things on the sides. It held it all, all day, for $25. We could access it all to change things all day. The backpacks were each 18x14x8, but we could squish them a bit in any direction we needed since they weren't completely overstuffed, but they were full.