you don't, you can dive naked if you'd like.... but you can also go snow skiing in the nude as well... it's all a matter of comfort. wetsuits help you retain heat and water removes heat 25x faster than air, so you DO get chilly faster in water... a great simple description is located here:
Scuba Divers wear wetsuits for the purpose of staying warm and protection. Wetsuits are named wetsuits because they get you wet. Water goes into the wetsuit and gets trapped. This trapped water is then heated up by your body by the escaping heat. This in turn keeps you warm. Also you know how when washing dishes your hands get soft. Well that happens to your body so rubbing against anything down there will for the most part cut you. The suits keep you protected.
They insulate against the cold water around you.
You don't always need a wetsuit, it is just in winter or cold countries you would wear one. It is too cold even unbearable without one so that's why you would need a wetsuit!
they need protection in water from dangerous animals also there is a problem in breathing so they carry gas cylinder.
warmth and protection
The collective noun is a bubble of scuba divers.
scuba divers
Many people use a SCUBA suit for diving. Sport divers, police divers and some Navy recovery divers.
Free divers do but scuba divers do not need to. Scuba divers take their air with them and would have no need to hyperventilate.
They swim
seebees
In the Water....
scuba divers
Marine biologists conduct extensive research on the organisms that live in various bodies of water. These scientists often wear scuba gear, wetsuits, protective gloves, and safety glasses for their occupation.
Scuba - self contained underwater breathing apparatus
Scuba Bob's Ocean Quest - 2006 Fearless Divers Scuba Rangers 2-7 was released on: USA: 2007
Scuba regulators, also called 'diving regulators', are vital for scuba divers to properly obtain oxygen from a tank. Regulators are available for purchase through diving specialty stores such as Prime Scuba, House of Scuba, and Divers Direct.