That positioning can cause backscatter and may be missing the target. In quite a few of your shots it looks like the strobe is angled wrong, so it puts out all its power to try and get enough light to the target, but its still too far out anglewise so it does a full dump. The anemone one is almost OK, so I dont think you're too far off, some of this is just practise and experimenting more.
With the Inon strobe turned off, try taking a picture of something with the camera in the housing and see how much light is getting through from the camera flash. Ideally you dont want any as it will increase backscatter. IF there is any, use some black tape on the inside of the housing to block off where its getting through, but that none of it is on the controls. Make sure the magnet is off the strobe - it will only matter if the strobe is set to 'manual' in theory.
Again, do some experiments above water, your real issue here is to simply methodically work through the combinations to find the ones that work to get the strobe to put out the right level of light and see how things are working. Find a target that you can take about 50cm away (eg a tennis ball, but pros use rubber duckies) in an indoor setting with a constant light level, and take a picture with the strobe pointing at it, dont change the distance from the subject, and only change the strobe angle if its obviously missing the target when its going off, then keep the strobe angle the same for every shot once it is hitting the target - set camera dial to M for manual, set to f8 and shutter at 1/250th, ISO to 80, and you probably need to be in 'macro' mode if the target is that close. In this mode its just telling the strobe to go off, and the strobe settings should then decide how powerful the strobe output is, which will hopefully simplify things.
Set your strobe on 's-ttl', and the other dial set to 'B' or 2.8 to start with, then take a picture and see what it looks like - it will probably be fairly dark but it doesnt matter as long as we can vary the strobe output using the other dial.
Try changing the dial to 2, 2.8 and 4 and take pictures with each and see if the light output changes, try more settings like 5.6 or 8 on the power dial or less than 2 if it seems like some level of lighting change is occurring - hopefully you can find settings that make things very dark or very bright.
DO NOT CHANGE the fstop, shutter speed or ISO on the camera, only muck around with the strobe settings to see what you can get as a result. Going by the posted pics variation in settings I suspect a lot of your problems are happening because you change too many things at a time, eg changing strobe settings and camera modes at the same time. The only thing you should be needing to change is the strobe in order to get the right level of light output from it. If something looks right, take another pic without changing anything to see if its consistent. Make sure you give the strobe time to recharge, and dont overheat it as said previously. Once you can get it to light reliably at a particular set of settings, and can reliably vary the light output by changing the strobe power, then start experimenting with changing the strobe angle and seeing what happens when you do. Ie change angle, then experiment with changing the power level for that particular strobe angle to see what happens, try another angle etc.
One thing that Inon does is make it so the direction you turn the power level dial will increase power under one mode and decrease it under the other mode which can confuse things, and the 'zero point' changes with sttl and manual as well. This is why Im telling you to experiment with turning the power dial both ways to see what happens.
If none of this works, say whats happening - all too bright, or too dim, whatever and post a couple of pics with all of the settings Ive listed, ie both camera and strobe settings for each pic.
Google found me several u/w photographers in NZ, you could also contact PADI and ask them for anyone who is teaching u/w photo courses, they should be around. What city are you in?
Otara
