Choosing a diving suit can be a perplexing task. If you’ve dived in the exact same conditions before (and kept a note in your log book) then it should be easy. But what if not? Here Jonas Arvidsson offers a simple explanation of the options available.
A Lycra suit is an elastic suit that is basically a swimming suit that covers part of (i.e. a rash vest), or the whole body. This gives hardly any protection against cooling, it is just a physical barrier against the sun and jellyfish stings. It can also be used under a wetsuit for easier donning and possibly reducing water circulation.
Shorties are suits with short legs and short or no sleeves. They protect the torso to some extent from cooling. A shortie works well for low-intensity diving in tropical climes, but if you are going on a dive trip for a few days and make three or four dives per day you may become uncomfortable with so little thermal protection. If you only intend to make one dive per day in tropical areas, you may not need a diving suit. But it is good to wear a t-shirt to avoid abrasions from your BCD.
A full wetsuit reduces water circulation in the suit, especially if it is of a good design and it fits you well. In cooler conditions, it can be supplemented with a hood as we lose a lot of heat from the head and neck if we do not protect these body parts. They are made in many styles and different thickness in different parts — e.g. legs and arms with 3 or 4 mm neoprene for increased mobility. It is impractical to use thicker than 7 mm material, so that is the only choice for colder water. Fixed hoods reduce water circulation in the suit as well as heat loss at the head and neck, but most suits have a separate one. Some models of thick wetsuits have a two-piece design — a jacket worn over a pair of long johns. This way you get double insulation over the torso.
A semi-dry suit is usually made of 7 mm neoprene with cuffs at the ankles and wrists, and a waterproof zipper. The hood can be fixed or separate. The aim is to minimise water circulation in the diving suit.
As indicated by the graphic above, a drysuit has the widest temperature range — especially a membrane suit, because the only real task this has is to keep you dry. The insulation is determined by the amount and type of clothes worn underneath. Another advantage of a drysuit is that you are dry when you remove the suit, which means that you do not risk cooling further after a dive.
For more detail about each type of suit, the options available on them and the materials they are made from, please buy my book.