Underwater Experience with S40 and WP-DC300

In absence of a dedicated topic on underwater usage of Canon cameras, I'd like to collect experiences with S40 and its waterproof case WP-DC300.
My major problem is fogging.
I mediterranean sea, below aroound 12 meters temperature of water drops down to 15-17 °C so causing fogging inside the case. I tried with antifogging liquid, but no info from Canon how to use it (Canon on its site suggest the use of silikagel bags).
I tried with air conditioning of car. It reduced the problem, but it still exists.
Does anyone knows other practical suggestions?

Finally few words about maximum depth of WP-DC300:
this week I have carried my camera at -36 in the first immersion and -39.2 meters in the second one.
In both cases - apart from fogging - I didn't experience any problems. Only at -39.2m I have noticed some little drops inside the case, but I don't know if it was due to fogging or due to initial leakage.

I use the DC-WP700 case and I haven't had any problem with fogging as I don't run into the temperature swings you are experiencing. Here in Florida I haven't had more than a 16°F swing in air to bottom temp (8-9°C), with most in the 5-6°F range.

Looking at my log book I've even been fortunate enough to dive in water warmer than the air temperature during what passes for winter here.

However to help keep fogging to a minimum, I do keep the housing in a shaded water bucket until it's time to hit the water. I also do use a gel pack to keep moisture down inside the case.

Perhaps a slower descent may also help?

Marc

Thanks for the suggestion of gel pack. Yesterday a friend of mine gave me one of these very rare objects and I'll try it in next dive.

I improved the situation with the following procedure:
1) I have applied on both camera optics and case glass (inside side) the antifogging liquid as uniformly as possible
2) I left the liquid to dry
3) during the tranfer to the diving center, I sealed the camera into the case with the air coming from the car air conditioning system.
...The result was no fog!
However I'm not yet completely satisfied of focusing level, which seems more degraded underwater than in air.
Did anyone experienced the same degradation?

p.s. I'd like to place a picture, but I do not know if it is possible and how to do it.