Basic Strobe Set-up/Placement

Okay I've seen picture set-ups for everyone's high dollar rigs with dual strobes using ballmounts with them set wide on each side. But if one was going to take shots with one DS-50 using the regular arm from Ikelite, should I place the strobe directly above (high or low) or beside (high or low) or wide (even). Is it better for the strobe to be even with the front of the camera lens or a little in front or behind. I plan on taking primarly pictures of people snorkeling underwater (I'll be maintianing position at 5 ft under water to shoot up), and then fish and reef shots at 40-50 feet when diving. Will these two different scenarios require different placement. Sorry for the basic question, I just have only seen the more elaborate set-ups and would like a little basic theory on strobe placement/angling. Is one constantly adjusting the strobe depending on which shot is coming available or do most keep their strobes set for most of the dive.

Fundamentally, you should have the strobe to one side and higher than the lens.

If you are shooting with a flat port, move the strobe forward to the end of the port. If using a dome port, have strobe behind or no further forward (i.e. even) than the back edge of the port.

That's the starting point. Look at the results. If you don't like the results, then move the strobe. Repeat until happy.

I started out with one strobe and then two strobes on a housed SLR. The strobes stayed in the same place, higher and to the side, for all my shots. It worked pretty well 90% of the time. Once I was comfortable with everything else on the camera, I began repositioning the strobe head for a different aiming line for different shots. Then I started repositioning the strobes via the arms for different lighting. This allowed both precise lighting just the way I wanted and also the ability to totally screw up a shot.

Start simple. Add complexity.