DRY-SUITS

In simple terms, there are 2 types of dry-suit: the membrane dry-suit and the neoprene dry-suit.  There are a few variants with crushed neoprene, which behaves like a membrane suit, but for simplicity I shall only refer these 2 types.

The disadvantage of a neoprene dry-suit is that the spongy neoprene behaves in the same way as it does with wetsuits: buoyancy and warmth are lost at depth as the neoprene is compressed.  Although more undergarments can be worn to counter this, this means that you are bulkier and more buoyant at the surface.  This in turn means that you have to use more lead weight in order to get down.  However, as stated above, much of this buoyancy is lost at depth so one has to put more air into your wing/stab and/or drysuit.  This increases drag and makes buoyancy control more difficult.

Wearing an excessive amount of underclothing will also restrict shoulder movement: an important consideration if you have to turn the pillar valves off behind you.

Because the trilaminate material of membrane suits is non-compressible, loss of buoyancy and insulation is not an issue.  That said, a baggy membrane dry-suit will also create too much drag and will “balloon up” in places where there is excess material.

In my opinion the best solution is to use a well-fitted membrane type suit with an automatic shoulder dump valve.  The cuff dumps appear to take longer to dump air from and mean that you have to keep raising your arm (annoying if using reel).  They also appear to leak more frequently.

Most suits in the UK come with Apeks inflate and dump valves.  Although Apeks do make a lower profile dump valve, SI-Tech make a better one that has a lower profile (won’t catch when taking set off) and flows more freely.  Like the Apeks it can be adjusted by turning the valve.  If you are concerned about having to dump air faster, then perhaps you should consider the SI-Tech.  Prices are comparable.

Putting/having pockets on the thighs of a drysuit are also a good idea.  Objects such as dive-slate, decompression tables, wet-book, strobe, line cutter etc. can all be stowed here.  They are very accessible (take a look where your hand rests when you stand up) and are out of the way of the important chest area.  Stab jacket pockets are generally harder to access and when full restrict the inflation of the bladder of the stab jacket, which then restricts breathing.  Avoid zipped pockets as they are harder to operate with gloves than a straightforward Velcro flap.