A suit designed to let people go underwater without their drowning or being crushed by the pressure of the water.
The first one was constructed in 1715 by John Lethbridge. It was made of wood and leather and was used for salvage work. Diving suits were in use from the early 1800s to the mid 1900s.
Today Scuba gear and light submarines have pretty much replaced them. The JIM suit, the JAM suit or the hardsuit, all of which look like bulky space suits, may still be used at times.
Diving Bell
Submarine
Aqualung
SCUBA
Submersible
Somtimes 'diving suit' can also refer to a wetsuit, drysuit, or diving skin, although these do not provide either air (in and of themselves) or protection from pressure.