Canyoneering

Canyoneering or canyoning is a dangerous sport. A person who goes canyoneering is a canyoneer. A canyoneer is a person who walks, swims, or rappels (climbs down ropes) into canyons. Sometimes these canyons are very deep and very narrow. Canyons that are very narrow are called "slot canyons". 
Dangers.
Canyoneering can be dangerous. Sometimes canyons flood (fill with water) when it rains. Accidents can also happen when a canyoneer is climbing down ropes. The rope can break or the canyoneer can slip. Sometimes canyons are too narrow to walk through, so you have to go back. Also, sometimes the water in canyons is so cold you can get sick. Many people have died in canyons.