Mark McCrill, age 15, of Storm Lake, Iowa, for his question:

WHAT DOES SCUBA DIVING MEAN?

Diving under water with the use of portable metal tanks and compressed air is called scuba diving. A diver using one tank can stay at a depth of 40 feet for about an hour.

The word scuba stands for self contained underwater breathing apparatus.

Scuba gear includes one or more tanks strapped to the diver's back, plus an ai.r hose and a device called a demand regulator. The demand regulator controls the flow of air so that the ai.r pressure within the diver's lungs remains equal to the pressure of the water.

Scuba divers wear a face mask, a wet suit, a weighted belt and swim fins. They use a snorkel and a flotation vest. The snorkel lets the diver conserve the air in the tanks while swimming at the surface and the flotation vest brings the diver quickly to the surface in an emergency.