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odern dry suits have a waterproof zipper for entry and exit which was originally developed by NASA to hold air inside astronautspace suits.[link widoczny dla zalogowanych] This complex and special zipper is one of the most expensive parts of the suit. 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 waterproof-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. Some snug-fitting suits may also use wrap-around expansion zippers that allow the suit to expand or contract to fit different size people.
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.
Before true-waterproof zippers were invented, other methods of keeping the suit waterproof at the entry point 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,[link widoczny dla zalogowanych] where the entry tunnel was at the navel. The Louisiana-based dry suit company Aquala still makes a "historical" diving suit of that kind.
Another type of entry featured 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.
Some types did not use a zipper at all. At least one make of old-type British frogman's dry suit 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 dry suit 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,[link widoczny dla zalogowanych], U.S. Divers Seal Suit and the So Lo Marx Skooba Totes suit, the Italian-madePirelli suit and the UK-made Heinke Delta suit and Siebe-Heinke Dip suit.[link widoczny dla zalogowanych] 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.