It takes practice to learn to breathe through the snorkel. If you do, you'll get a mouthful of water, and you'll have to blow out through the tube while you are under the surface. Then, you swim up to where the tip of your snorkel is above water, and that's the time to breathe in. Andrea swims through a hoop. That's the next step to underwater exploring.
Scuba divers use a tank of air, strapped on their bodies.
Underwater, they breathe through the mouthpiece. They can dive to where they see amazing things on the ocean floor. Kids can learn to scuba, too, at diving shops or at special Scuba Ranger classes taught through Scuba Schools International programs all across the USA and Canada. Most classes teach you first to snorkel, then you can advance to wear scuba tanks and do underwater diving. To begin, you will need a mask, snorkel, snorkeling vest, fins for your feet and, of course, a swimsuit.