Shooting in very low light

In St Martin last week my pix came out fine if I was shooting in good light. But when shooting inside a very dark wreck, the pictures came out almost black. Do i need a separate light source so the G2 can find focus before I fire the Ds125? Any thoughts?

Yes, you need a modeling light. Auto Focus works by contrast so to make it work you need to get some light on the subject in dim light or dark situations.