History of diving
Diving is very old. People dived holding their breath to get food, sponges and pearls. This is called breath-hold diving (also free diving).
To stay longer, people used a diving bell: a heavy upside-down container. Air stays trapped inside it, and the diver breathes from it.
About two hundred years ago the helmet arrived. A hand pump on the boat sent air through a hose to a heavy helmet and suit. Later, pumps became powerful machines called compressors.
In the 1940s a free-swimming air system was made: scuba. The word means Self-Contained Underwater Breathing Apparatus. The diver carries the air.
Since then divers have learned to use mixed gases, chambers and underwater homes for very deep, long jobs.
Diver aptitude: who can dive?
Aptitude means being suited for a job. A diver needs three kinds of fitness.
- Body: healthy heart and lungs, ears and sinuses that are not blocked, no fits or fainting. A doctor must check this.
- Skill: swimming well, and learning to use the gear.
- Mind: calm in a problem, careful, able to follow rules, and willing to dive with a partner (the "buddy").
A person with a cold, a sore ear or who has drunk alcohol must not dive. Good divers also keep learning and keep fit.
Types of diving
We group diving by how the diver gets air.
- Breath-hold (free) diving: no gear for air. Short and shallow. Used for fishing, sport.
- Scuba diving: air in a tank on the back. The diver moves freely. Common depth for trained recreational divers: up to about 40 m.
- Surface-supplied diving: air comes by hose from the boat. The diver wears a helmet or full-face mask. Used in harbour and construction work, because the air supply is large and a phone line lets people talk.
- Saturation diving: divers live in a pressure chamber for days and work at depths of hundreds of metres. They come up slowly only once at the end.
By purpose we also say: recreational, fishery work, scientific, salvage and rescue.
Try it
Open the 3D and tap the four types in step 6. Predict first: which type goes deepest? Then check the depth shown. At home, hold your breath and count seconds normally. Never practise breath-holding in water without an adult.
Key formulas and definitions
- Scuba = Self-Contained Underwater Breathing Apparatus
- Types: breath-hold, scuba, surface-supplied, saturation
- Seawater: pressure rises by about 1 atm for every 10 m of depth
- Fitness = healthy body + swimming skill + calm mind
Worked examples
1. Which type of diving would a harbour worker use to repair a pier for several hours?
Surface-supplied diving. The air comes by hose from the surface, so it does not run out, and the diver can talk by phone.
2. A diver carries a tank and swims freely at 25 m. Name the type.
Scuba diving. The air is carried by the diver, so no hose is needed.
3. Put in time order: scuba, helmet, breath-hold, diving bell.
Breath-hold, diving bell, helmet, scuba.
Common mistakes
- Thinking scuba is the oldest kind. Breath-hold diving is the oldest.
- Thinking aptitude means only a strong body. Skill and a calm mind matter too.
- Diving alone because you swim well. Always dive with a buddy.
- Thinking every diver can go as deep as any other. The type of diving sets the safe depth.