frogfish once bubbled...
There is a Sea&Sea dealer in the Adelphi mall on Coleman Street (the shop is called Divers Deams).
You will be able to find the Coolpix 5000 in many shops - try Sim Lim square for instance where you should be able to get a good deal
I doubt you'd find much in the way of UW camera gear at Sim Lim. Lucky Plaza (on Orchard Rd) has three dive shops in the basement and a couple of camera shops that carry Nikonos and Sea & Sea equipment. In spite of being on Orchard Rd., you can usually deal with shopkeepers in Lucky Plaza.