Welcome to the world of underwater photography $$$

. I would barely call myself an amatuer photographer but there is no real "cheap" way to take your SLR underwater. A good housing is going to
start around $2000 bucks by the time you put a port on it and get zoom gears. Then there are the strobes about $700-$1200 bucks each plus sync cords (~$100). The strobe arms are going to come in around $200.00.
You will have to start getting into pro cameras before the camera is actually worth more than the housing.....and even then. I went with Aquatica for my D70s and probably spent in the range of 3500 when all was said and done...that's with one strobe......that said I still love doing it.
There are others around here with better setup than I have but the price will only start to go up.
B and H photo has quite a bit of u/w equipement and will give you an idea of what your in for