As for working backwards, which is sort of how I approach things, you need to know your limits in post-processing. Which basically means being comfortable squeezing all that dynamic range into something that 'fits' a typical display via JPG. Take an image at base ISO, then ISO 400 and then ISO 800 and try boosting shadows and pulling down highlights in all three. I suspect you'll find a huge difference between base ISO and 800, and quite a lot of loss of range at 400. I lose the ability to pull down highlights pretty quick.
I learned that it is more important - on my cameras - to expose for the highlights. If you have something like a Sea Rod that gets bright hot spots, you'll want to pull down the strobe power and shoot at base ISO as much as anything. I'm not sure it does much good to just pull the strobes away farther (as opposed to reducing power), but certainly it doesn't help to have a strobe situation right next to a hot spot. For example, a strobe sitting close to white coral sands on the bottom may give you a hugely distracting element that would otherwise not have been there with a different placement. Of course this means recognizing hot spots to start with. I think it helps to give yourself assignments to shoot certain subjects when you see them and then practice post-processing on them in particular.
One thing that can help taming highlights from a strobe point of view is using diffusers, but you may or may not want a hard edge to the lighting for some scene you have in mind. Another is multiple strobes if you are shooting with only one.
If you have not heard of the concept of ISO Invariance, you might want to look that up and read about it. I summarize it as saying it is at least just as good to shoot at base ISO in the field and boost in post as it is to shoot at a high ISO in the field to see a properly-exposed JPG. Basically, if you are good a post-processing, you may get better results doing your own exposure boosts in post as the camera would do for you in-camera.
In all cases it will become obvious to you in post that you can do more pulling and pushing at lower ISOs than higher. I find it amazing how fast my images lose dynamic range by ISO 800. When I'm trying to color balance and push shadows and pull highlights, there just isn't any room left for adjustments as the high ISO has already boosted everything to the limit. It's like the difference between post-processing a RAW file and a JPG.
One thing you will find is that you become suspicious of using high ISO's. They work fine when contrast and dynamic range is low, but underwater subjects lit by strobe are frequently wide dynamic range subjects. Learn to shoot at base ISO first. Nothing tames a highlight better.
Other subjects do have low dynamic range. They look pretty flat because there are not very dark and very bright areas in the same frame. Doesn't much matter if you shoot ISO 3600 then. But if you are shooting a barracuda (or any silvery-scaled fish) at high ISO you may have to give up on recovering data from the highlighted areas where the strobe reflects off the scales.
Sometimes you just can't win. I learned early on that there are shots not to take, because the lighting is poor. Or maybe the subject is compelling, but conditions aren't good. Just don't expect too much. Here are two shots that might help explain. Each has defects. One is lit by strobes that were too far away, the other is what you get in ambient.
The ambient exposure is very grainy and has loss of detail in the subject. The flash-exposed version suffered from unfixable hot spots (not enough dynamic range in the image to pull down the highlights) and loses the background. I just could not get close enough as the subjects were skittish and keeping their distance. Pretty much any time I'm shooting wide angle I'm having issues below 30 feet or when the sky is cloudy. Strobes can never light everything, and then I have color balance issue between subjects and backgrounds.
Some of the solution is a slower shutter speed, but that gets into other problems, meaning blurry fish. I really try to shoot at 1/160th as a sweet spot - faster loses too much strobe power, or in some cases hits a sync limit and gives a black line across the frame. Shooting slower leads to blurry fish. I'll go slower, but it depends entirely on the subject. Sometimes you use a very lot shutter speed, take 20 shots, and hope one of them is OK.
I think many people never really try to understand and solve the issue of highlight detail. They just let hot spots blow hot and ignore them.
It's a challenging environment to shoot in. Make it much more fun when you get a good result.