The main difference between drysuits and wetsuits is that drysuits are designed to prevent water entering. This generally allows better insulation in drysuits making them more suitable for use in cold water. Drysuits can be uncomfortably hot in warm or hot air. They are generally more expensive than wetsuits.
To stay warm in a membrane suit, the wearer must wear an insulating undersuit, today typically made with polyester or other synthetic fiber batting. Polyester and other synthetics are preferred over natural materials, since synthetic materials have better insulating properties when damp or wet from sweat, seepage, or a leak.
Reasonable care must be taken not to hole or tear membrane drysuits, because buoyancy and insulation depend completely on the gas pockets in the undersuit. The drysuit material offers essentially no buoyancy or insulation itself, so if the drysuit leaks or is torn, water can soak the undersuit, with a corresponding loss of buoyancy and insulation.
In warmer waters, some wearers wear specially designed membrane drysuits without an undersuit. These are different in design, materials, and construction from drysuits made for cold water diving.
Membrane drysuits may also be made of a waterproof and breathable material to enable comfortable wear when out of the water for long periods of time. Sailors and boaters who intend to stay out of the water prefer this type of suit.
Modern dry suits have a waterproof zipper for entry and exit which was originally developed by NASA to hold air inside astronaut space suits. The zipper is commonly installed across the back of the shoulders, but can also be found diagonally across the front of the torso, on the side, or straight down the middle of the front or back.
There are many zipper arrangements in use because the zipper is very rigid, and cannot stretch at all, which can make it difficult for a user to get into and out of the suit. The zipper opening is often quite small, since a large zipper makes the suit stiffer and more difficult to use. Some complex zipper arrangements that wrap around the neck or chest let the suit swing open with a flap or hinge point.
Dry suits may also be fitted with an extra waterproof zipper "fly" to let the user urinate when the suit is worn for long periods. Some snug-fitting suits may also use wrap-around expansion zippers that allow the suit to expand or contract to fit different size people.
Before waterproof zips were invented, other methods had to be devised, with the most common being a long rubber entry tunnel which would be flattened shut, then rolled together from the sides and finally folded and clamped with a metal clip. An early example was the Sladen suit, where the entry tunnel was at the umbilicus. The Louisiana-based drysuit company Aquala still makes a "historical" diving suit of that kind.
Another type was a rubber tunnel that protruded through a normal cloth zipper. The tunnel would be rolled shut and the zipper closed to hold the roll in place. At least one make of old-type British frogman's drysuit was one-piece with a wide neck hole for entry; the bottom of the hood and the edge of the suit's neck hole were held together by a large circular steel clamp around the neck; there was a watertight seal in the bottom of the hood. Two-piece drysuit designs in full length for year-round use and "shorty" styles for summer-season use were also common in the 1950s and early 1960s. Two-piece suits of the period include the American-made Spearfisherman frogman suit, U.S. Divers Seal Suit and the So Lo Marx Skooba Totes suit, the Italian-made Pirelli suit and the UK-made Heinke Delta suit and Siebe-Heinke Dip suit. These suits were sealed at the waist by rolling together the excess material at the bottom of the shirt and the top of the pants. A cummerbund, rail, or surgical tubing was sometimes provided to make the seal more waterproof. A modern version of the two-piece drysuit is manufactured by Customworks of Idaho. Though lacking such features as valves and zippers, these suits still have certain advantages over their modern counterparts. For example, they are cheaper, less bulky, more easily repaired and the footed pants could also double as fishing waders.
If it is not important to have exposed bare hands, permanently attached heavy rubber gloves or mitts can help make getting in and out of the suit much easier since there is no need for the suit to tightly seal around the wrists. Instead, the wearer can slip into the attached gloves as if they were a loose-fitting coat sleeve.
Full-hand diving mitts can be sometimes useful in extreme environments such as ice diving.
Three-finger mitts are a midpoint between gloves and mittens. In the three-finger mitts, the fingers are arranged like the science-fiction Vulcan salute. This provides slightly better hand-grasping dexterity while still permitting heavy insulation around the hands.
Separate (non integral) neoprene hoods for use with a dry suit are different from wetsuit hoods, because they cannot be tucked inside the suit at the collar, as this would compromise the neck seal; with these the wearer's head gets wet, which would be a risk when diving in contaminated water.
For a commercial environment where the option of interchangeable boots for different sizes of feet is desired, the legs of the dry suit can also be fitted with attachment rings (described below). Some commercial divers order their suits without boots and install rubber work boots such as those used by miners or [[Firefighter|firefighters].
These are typically only seen on professional and commercial diving suits. They allow separate neck seals, gloves, and boots to be joined to the suit with a watertight seal. The attachment ring system uses a support ring inside the suit and a clamping band outside the suit to tightly hold the suit and the separate hood/boot/glove together. They were also used with the neck seals of some old British frogman-type drysuits (see above).
The support ring can optionally be slipped into the sleeve of a regular drysuit that has wrist seals, to temporarily put watertight rubber gloves on the suit, or the wrist seals can be removed and the inner support ring is permanently attached inside the sleeve. The support ring may be a large one-piece unit that can be slipped over the head/hands/feet, or it may be split into halves that can be directly installed up close around the neck/wrists/ankles.
Attachment rings let a commercial diver change his suit to best perform the task at hand. Wrist seals can still be used with an attachment ring suit; they are mounted onto the ring like a pair of gloves.
Vent valves can be automatic, operating as pressure relief valves, or manual, where the diver must raise the valve to vent. Automatic vents are generally at the shoulder, and manual vents are at the wrist. Some older drysuits have no vents, but the diver must lift one of the wrist seals or the neck seal open to vent the drysuit. Surface dry suits are not inflated, and must be vented to remove most of the gas inside.
Because the air inside the suit is compressed as the diver descends, a modern diving drysuit also has a gas inflation valve, which lets the diver control the buoyancy of the suit by injecting gas from a diving cylinder to avoid the suit from being squeezed tightly and painfully onto the diver's body during descent. The sensation is similar to being pinched, but all over the body. Suit squeeze can also hinder the diver's movement and make swimming more difficult.
Some old-type frogman's drysuits had a small "jack cylinder" to be inflated from, or the frogman (who was using an oxygen rebreather and so limited to about 30 feet (9.144 m) depth) had to put up with the suit squeeze.
Normally, the gas used for dry suit inflation for diving is air from the primary breathing cylinder. When divers breathe helium-based gas mixes such as trimix, they often avoid inflating their suits with the helium-based gas due to its high thermal conductivity. They often carry a separate cylinder for this purpose; generally it contains air, although sometimes argon, which has lower thermal conductivity, is used. Pure argon cannot be used as a breathing gas. Alternatively, some trimix divers inflate their suits from a decompression cylinder containing a nitrox blend.
In surface dry suits, the wearer normally never dives deeply underwater, and is not concerned about neutral buoyancy, so there are no air valves on a surface drysuit.
Before putting on the drysuit, the diver puts on a condom catheter, which is similar to a condom except that it is made of thicker material with a cuff or adhesive ring to prevent it from slipping off, and its end connects to a built-on drain tube. After putting it on, he attaches the end of the tube to a drain hose in the crotch of the suit. This drain hose leads to a vent opening just above a knee, and may also have a one-way valve (P-valve)to prevent ocean water from flowing back in if the hose gets disconnected.
Dry suits are used for windsurfing, kitesurfing, kayaking, water skiing and other surface water sports where the user is frequently immersed in cold water. These suits are often made from very lightweight material for high flexibility. Membrane type suits are commonly used in the spring and fall with moderate water temperatures, but Neoprene and hybrid dry suits for surface sports are preferred in cold water. These provide greater thermal protection in the event of a leak. The ability to swim for self-rescue in these types of suits is important to water sports users that do not use a boat. A neoprene bottom also is less likely to allow trapped air to collect in the legs, causing the wearer to tend to float head down in the water.
Some types of latex seals may be liable to rubber perishing.
Latex seals are somewhat elastic, but can be easily torn if overstretched. Powdered talc can help the seals slide on easier.
Neoprene seals are often used. They are less waterthight than latex, but can be repaired easily by the user.
Waterproof zippers need the two rows of open teeth to be reasonably lined up in front of the pull, for the zipper to slide without excessive effort. (Because of their construction waterproof zippers require two or three times as much pull as regular zippers to close.) It is best to hold the opening together as the zipper is pulled shut to prevent misalignment that can permanently damage the sealing edge. For this reason zippers across the back of the shoulders or down the back of the suit are almost impossible for one person to close properly by themselves, and yanking harder to try and force the unreachable zipper closed often just results in misalignment and permanent zipper damage.
Damage to the upper part of the suit can cause a sudden venting of the air, resulting in a total loss of thermal insulation in membrane suits and sudden uncontrolled descent, followed by water/chemicals seeping in.
Drysuit wearers wearing loose baggy suits need to keep their legs at level or below their waist. When inverted, with the legs above the waist, the bubble quickly moves top the highest point, the legs.
If the suit is being used correctly, the bubble is small and its movement is not important. The bubble may be large if a diver has ascended without venting the suit or the diver is over-weighted and extra air has been put in the suit to make the diver neutrally buoyant. The movement of a large bubble can be a problem; it balloons the legs and it may inflate the thin rubber booties causing the fins to pop off, losing them in the water. Also, as the drysuit vents are most often situated at the top half of the diver, it is impossible to vent the suit while inverted. If the diver is positively buoyant, there is an increased risk of a fast ascent to the surface.
The size of the bubble can be minimised by being correctly weighted and venting the suit on ascent. Some divers ensure that the bubble remains at the top of their body by using the buoyancy compensator to counteract any excess weighting and keeping the minimum air, to avoid squeeze, in the suit.
For an inexperienced diver, ballooning of the legs can cause a loss of control that may to lead to panic and an inability to flip upright again. The recommended solution is for the wearer to bend at the knees, reach up and grab the legs, do a somersault to flip upright again and vent the suit if needed by opening the neck seal.
It is not a problem for close-fitting neoprene suits, or hybrid suits with neoprene bottoms, which prevent air from easily moving into the legs of the suit. Wearers of baggy surface drysuits can mitigate the problem by venting out as much excess air as possible before entering the water. This is typically done by crouching down and leaning forward, wrapping the arms around the knees, and then having an assistant zip the suit shut while it is stretched out tightly. Excess air can also be "burped" out of the neck seal. Some baggy suits have elastic "gaiters" that can be pulled snug around the legs to help prevent this inversion event from happening.
|Maker||Make||1/2 piece?||When available||Notes||Info link|
|Pirelli||Pirelli Diving Suit||2||from 1930's||designed for Italian frogmen|
|Siebe Gorman||"Frogman" suits||1 or 2||World War II & after|| designed for British frogmen|
|Spearfisherman||Spearfisherman Frogman Suits||2||1945 & after||designed for USA frogmen|
|U.S. Divers||U.S. Divers Seal Suit||1 or 2||from 1953 or before||varIous|
|Heinke||Heinke Delta Suit||2||from mid-1950s||rubberized stockinette|
|Healthways||Healthways Carib Suits||2||from 1955 or before||pure natural rubber|
|Bel-Aqua||Bel-Aqua Dry Suits|| 1|
|from 1955 or before|| a 3-ply material, front tube entry|
a 3-ply material
|unidentified||Seamless Suits||2||from 1953?||dipped pure latex|
|made by or for Lillywhites||Lillywhites Mid-1950s Suits||2||from 1955 or earlier||rubberized stockinette|
|So-Lo Marx Rubber Company||Skooba-"totes" Suits||2||from late 1950s||all-rubber|
|Siebe Gorman||Siebe-Heinke Dip Suit||2||1964 & after||dipped latex|
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