What is a river tube?
Water. Tubes for use as towables on water are generally not true inner tubes but rather specially designed tubes for the purpose of recreation. These tubes are often fairly durable and come in either donut or disk shapes. A tube is a pipe shape, a cylinder with a hollow space inside. If you’re like most people, you sip your milkshake through a straw — a long, plastic tube. Chemists use glass tubes in labs, and plumbers work with pipes — tubes made of plastic and metal. Another kind of tube is the rubber one inside a tire.