Figure 19. Hard hat diver. (Westinghouse photo) 
gories: dry suits, intended to keep the wearer dry, 
and wet suits, which have a thin, relatively 
stagnant layer of water between the swimmer’s 
skin and the suit. 
The dry suit still is preferred for extremely cold 
water. It usually is made of rubber, relying on seals 
at waist, neck, wrist, and ankles to keep water out. 
Woolen underclothing may be worn inside. A 
major disadvantage is that a tear admitting water 
practically destroys the suit’s insulating effect. 
More sophisticated dry suits (constant volume 
suits) now are available; a regulated gas supply 
keeps the inside of the suit slightly above ambient 
pressure and prevents squeeze as the diver changes 
depth. 
The wet suit is made of closed cell neoprene 
sheets, and consists of a close fitting jacket, 
trousers, hood, gloves, and socks. The layer of tiny 
gas bubbles entrapped in the closed cell neoprene 
between the cold water and the diver’s body 
provides insulation. The thin film of water inside 
the suit is virtually stagnant and rises very quickly 
to skin temperature. Because the flexible suit 
material contains gas in closed cells, the increasing 
pressure of depth compresses the material, dimin- 
ishing its insulating value and the diver’s buoy- 
ancy. 
Heated suits are among the most recent devel- 
opments; they contain electric heating elements or 
tubes for hot water circulation (Figure 20). One 
Figure 20. Model of hot water circulation suit. 
(Westinghouse photo) 
VI-S9 
