Scuba diving offers a respite from the relentless pressures of city life, especially its noise, dirt and air pollution.
It also offers the chance to see the enchanting sea creatures that share more than two-thirds of our planet's space with us.
Contrary to conventional wisdom, scuba diving is not dangerous if you are well-trained, have the appropriate equipment and stick to the rules.
It is also a fun sport suitable for most people.
'Scuba diving is even possible for people with physical disabilities,' says instructor Daniel Yau, who has difficulty walking as a result of contracting polio when he was a child.
'The buoyancy of water makes the body more weightless and this frees disabled people from many of their disadvantages of movement.'
The term 'scuba' stands for 'self-contained underwater breathing apparatus'. Scuba-divers need various pieces of equipment, including a buoyancy control device, mask and snorkel, fins, tank, regulator and wetsuit.
While physical disabilities are not such a concern, Yau says people with conditions such as heart disease or diabetes should not dive.
'If you want to dive, you must have good health,' he says. That means regular aerobic exercise, and avoiding smoking and drinking.
These simple health tips should not be taken lightly as they can be a matter of life or death under water.
For example, if you are overweight, there is a greater risk of decompression sickness. According to Yau, fat tissue absorbs nitrogen easily and, if the concentration of the gas in your body is too high, it may lead to the formation of nitrogen bubbles, which could ultimately cause a stroke.
If you feel that you are physically fit and ready to flex your muscles under water, Yau offers the following advice.
First, your breathing under water must be slow and deep. Don't hold your breath, especially when you are ascending. Doing so will over-extend your lungs due to changes in water pressure.
Second, return to the surface slowly. For recreational divers, the cardinal rule is to not ascend more than 18 metres a minute. This will lower the risk of decompression sickness.
Among Yau's favourite diving spots in Hong Kong are the waters near Pak Lap, home of the clown fish - real-life Nemos.
Other hot diving places include Sharp Island (Kiu Tsui Chau) near Sai Kung and Port Island (Chek Chau) in Mirs Bay (Tai Pang Wan).
'I've seen lots of different creatures while diving, like sharks, sea turtles and many types of fish,' Yau says.