There are a variety of types and sizes of cave packs. They are dragged, dropped, submerged, and otherwise treated rather brutally. In most cases packs with zippers won’t function for very long, so draw closures, buckles, or clips that are mud and moisture resistant tend to work better. Not all caves are wet, so packs don’t necessarily need to be waterproof, and any waterproofing is likely to fail in time, but for wet caves packs should either have waterproof functionality that is maintained, or be equipped with drain holes.
Some European cavers carry nothing more than a small bolting bag with just a few fundamentals, but for most cavers a day-pack will have a volume from 500 to 1,500 cu-inches (8 to 25 liters). For a basic horizontal recreational trip a pack on the low end of that range is enough to carry a little food, water, a small repair and first-aid kit, and some spare batteries and headlamp. A survey trip in a vertical cave may require a pack on the larger end of that range. For more involved project work such as rigging or digging, then a pack in the 1,500 to 2,500 cu-inch (25 to 40 liters) range may be necessary. Typical camp packs range from 2,500 to 3,500 cu-inches (40 to 60 liters) and must be able to carry sleeping bags, sleeping pads, stoves, extra food, tarps, etc.
There are a few fundamental pack types designed specifically for caving:
These are loosely based on one of the classic original cave packs - the army surplus gas mask bag. The standard in US caving for many years was the Lost Creek pack, but sadly they are no longer being produced. A very similar pack, in various sizes and configurations, is now made by OnRope 1. Side packs have two wide adjustable straps and typically five D-rings that allow the packs to be worn as a traditional backpack, fanny pack, or side-pack. The side-pack configuration is the most popular and is a very efficient way of wearing a pack through lots of chimney climbs and crawls.
The standard pack used in most of Europe is a round or oval bag with two shoulder straps and a drawstring closure at the top. Packs such as the Petzl Classique define this category. These carry a lot of gear, are simple, light and durable, and are easy to drag or tether in crawls or on rope respectively. Most larger camp packs are of the tackle bag variety, and some, like those from GGG, have a roll-top closure instead of the drawstring variety.
Some cavers put a shoulder sling on a dry bag and use this as a cave pack, but they have a tendency to develop holes quickly, and the dry closure no longer serves a purpose. A significant modification of the dry-bag roll closure bag is the Swaygo, designed by Scott McCrea. The Swaygo has a very low profile that allows wearing it in very low-ceiling passages. It is made of a urethane coated fabric that is extremely abrasion and puncture resistant, and it has an ingenious and highly adjustable shoulder strap system.