I am curious to know why flying over water (day or night) is considered so dangerous, so risky, when every capital city GA airport has Ranges nearby which must be crossed which I consider should be treated with equal respect. In Darwin's case, maybe no Ranges, but certainly the waterways nearby contain things with teeth that I would rather not mess with.
If you are trained, current and confident, to fly an aircraft (single or twin) in VFR, IMC, over water, over Tiger country, day, night, upside down, then go for your life. But if you are not trained, current or confident (Pick any one of these three) then may I suggest - don't.
But I really would prefer if you didn't let your standards and your limits stop me.