Scuba diving is an activity in which you swim underwater for extended periods using Self-Contained Underwater Breathing Apparatus, hence the acronym SCUBA, or Scuba.
Scuba diving is an excellent way to see some very beautiful sites: Tropical coral diving sites with their colourful sea life are the most famous but other scuba diving attractions include tropical and temperate rocky reefs, shipwrecks, caverns and caves.
Scuba diving can also be a very relaxing sport and in many places it's very beginner friendly. Many dive sites are accessible (under the care of an instructor) after a short briefing and training dive. You can learn to dive far more quickly than you can learn snow sports, for example, and a high level of fitness and strength is not always necessary. It's also suitable for people with a number of physical disabilities. As long as you can use the breathing equipment and are able to successfully propel yourself underwater you may be able to dive.