Hi, Namaste,
You are welcome

and thanks for the compliments. :blush:
I bought the Sunpak G-flash. It has a guide number up to 22 - I typically do macro shots and use 3 to 5. The strobe is adequate for whatever pictures I wanted to take during day dives. At night, the S1 needs a light to help it to focus. This strobe does not have a target light so I use my torch to do that and it sometimes result in a "bright spot" in the pictures.
The camera housing was still a little buoyant after adding the strobe. (Canon.com.sg recommends 4 pcs of weights for the housing. Unfortunately I couldn't find any shops in Singapore selling those weights). As for the len, I bought the Inon UCL165 M67 close-up len which gives 2 x magnification. In order to mount the len, you need to get the Inon M67 mount base.
The shutter lag was a bit annoying initially. By the time the picture was taken, the fish had moved away. And now what I have done is learnt how to approach the subject very, very slowly. And it works.
As for video, I had only taken the video once... I think it was a 1.5 minute video of a manta ray. I played with the zoom while filming and the resolution was much better (my PC crashed and I lost the file. Otherwise I could email it to you) compared to the still shots.
Since I take mostly macro shots, I was considering upgrading to S2 but the Canon websites do not indicate if a housing is available. In the end I decided that the macro len works well enough (by the way you can stack multiple lens and since it is wet-mountable, you can swap macro/ wide-angle len underwater!) and I can save the money for another dive trip!
Hope this helps!
Cat.