Diving with a DSLR is complex, cumbersome and expensive. Ikelite housings start from $1500 + about $200 for a port per each lens.
If you are not a professional photographer and travel weight is a factor for you, we would recommend that you consider diving with a compact camera.
With that said, no camera compares to the optical quality, low light performance and speed of a DSLR and as such if you can afford such a housing and bear the oversized luggage , DSLR is your preferred choice.
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