A dry bag is a type of bag which seals in a watertight manner. Dry bags are often used in kayaking

Kayaking

Kayaking is the use of a kayak for moving across water. Kayaking and canoeing are also known as paddling. Kayaking is distinguished from canoeing by the sitting position of the paddler and the number of blades on the paddle...

, canoeing

Canoeing

Canoeing is an outdoor activity that involves a special kind of canoe.Open canoes may be 'poled' , sailed, 'lined and tracked' or even 'gunnel-bobbed'....

, rafting

Rafting

Rafting or white water rafting is a challenging recreational outdoor activity using an inflatable raft to navigate a river or other bodies of water. This is usually done on white water or different degrees of rough water, in order to thrill and excite the raft passengers. The development of this...

, and other outdoor activities where sensitive items would otherwise get wet as well as extreme sports such as skiing

Skiing

Skiing is a recreational activity using skis as equipment for traveling over snow. Skis are used in conjunction with boots that connect to the ski with use of a binding....

 and snowboarding

Snowboarding

Snowboarding is a sport that involves descending a slope that is covered with snow on a snowboard attached to a rider's feet using a special boot set onto mounted binding. The development of snowboarding was inspired by skateboarding, sledding, surfing and skiing. It was developed in the U.S.A...

. They are often a construction of plastic film, plastic-coated fabric or waterproofed fabric which is formed to create an impermeable, water-ingress protected bag. When using a dry bag, it is vital to ensure the roll top closure is folded at least three times, to create a watertight seal. Construction techniques include welding, sewing (where a seam-tape is used to seal over any needle-holes) and gluing.