Carol --
I recently read a very comprehensive article on this subject -- may have been
in Rodale's or perhaps Alert Diver -- which debunked many wetsuit myths.

Based upon information therein:
Adding fluffy things under a wetsuit would probably have the OPPOSITE effect to
the one you desire.  Wetsuits keep you warm ONLY because they insulate with gas
trapped within the neoprene.  They lose much of their insulating properties at
depth due to compression.  That's a fact of life. Wetsuits are, by definition,
WET inside.  Therefore your body is constantly subject to the cooling effect of
the water against your skin.  Adding woollies, or a lycra suit or a Polartec,
under your wetsuit simply increases the amount of water between you and that
layer of insulation.  Therefore you become colder.  Such techniques work well
ABOVE water (due to the insulating properties of trapped air), but not at all
UNDER it (due to the cooling properties of water).  Drysuits keep you warm by
trapping air between you and the ocean.  Wetsuits "insulated" with Polartec or
woollies would just allow more water to circulate, cooling you down.

According to the article, the warmest wetsuits for the same thickness are the
ones which allow the minimum of water between you and the neoprene.  The newer
suits with "skin in" surfaces which "cling" to your skin should do the best job
of this.  Water-seals at ankles, wrists and neck help by reducing the
circulation of water from outside the suit to inside, and vice-versa.

Since a significant portion of heat loss is from the scalp, a close-fitting
hood (as Strike and others have mentioned) might do the most to reduce
additional heat loss.  In water as cold as you are contemplating, however, not
much is going to keep you warm except a dry suit!  (And, trust me, in a 5mm or
7mm wetsuit you ain't going to be able to surface dive without weights anyway!)

Dive safe [\],
-Dave

Carol Reid wrote:

> I'm taking some snorkellers out in Loch Fyne in June when the water  temp
> will be around 12C (54F)   They will be hiring wet suits and in the past I
> have worn a dry suit but this is not v good for snorkelling and impossible
> to surface dive to 3/5m  unless weighted (and then how do I come back up?)
> so I thought about wearing my own 5mm wet suit.   Last year in California I
> was chilly in 16C - so in 12C.......  Brrrr....
> So how can I, without any huge expense, beef up the thermal properties of a
> wet suit?
> Wear woollies underneath?

--
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Dave DeBarger
[log in to unmask]

"ASSETS make things possible.  PEOPLE make things happen!"
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