I have had a sea & sea dx1g with a pair of ys110 strobes about a year now and am very happy with them. Prior, I shot ambient light video for over 10 years (sony & amphibico rig) and recognized that no strobes means shallow still shots only (less than 30 feet down). My video rig could pull in enough light down to 60 feet (video is less demanding).
So if you are SERIOUS about stills, you need strobes. In general onboard flash won't work because of back scatter. If you want to shoot macro, you need 2 strobes to get balanced lighting.
If all you want is happy snaps, then the new generation of strobeless point and shoot cameras are great! I have seen lots of excellent photos come from these types of cameras over the last few years. The price point is also great. Just don't expect to get deep, wide angle, macro or night shots with them.