You can generally say that Macro Shots are taken with strobe light only while Wide Angle Photography mixes strobe light on the subject with available light in the background. Generally. Because just like more and more people are bringing Macro Photography into Wide Angle by using Close Focus Wide Angle Techniques and Mini Domes you can bring a bit of Wide Angle into your Macro Photography by incorporating available light in your shots. This not only creates a new look and feel to your Photography but is also a lot of fun.
The basic idea of this technique is very simple: You shoot your subjects (=Foreground) with strobes and bring available light into your background by using open apertures, longer shutter speeds, possibly higher ISO and suiting angles.
The best way to start this technique is to try it out on a “easy” subject like a free swimming fish or something sitting on a whip coral or a very exposed position with a lot of water behind it. Shoot it like you would like to achieve a black background but open your aperture as far as your desired DOF (depth of field) allows and then make your shutter speed longer until the metering in your viewfinder of on your screen shows two to three steps underexposed. If the shutter speed is then too slow for your to achieve a steady shot, you can bump up your ISO to make your sensor more sensitiv to light and achieve the same exposure with a shorter shutter speed. The result will be a blue or greenish background – depending on the water colour and your angle. With the sun in the back you can usually achieve better water colours.
But even less exposed subjects on the seafloor can be shot like this … It works with Frogfish, Seahorses, Nudibranchs … basicly all you need is the possibility to get low enough to gain some background. The key here is to combine that very low angle (to get background not lit by the strobes) with intelligent strobe positioning. Either you want to separate the subject from the background (by using small bumps on the bottom) or to place your strobe in a way that it evenly fades into the ambient light.