Brrrrr, that water looks cold!
Getting good shots of divers is, I've found, one of the hardest things to capture underwater. You have to find people who are prepared to spend the time and energy posing ("modelling") so that you get shots with their eyes open, feet/fins/legs nicely posed, bubble streams and, a vague, happy, interested smile on their faces. Have a look at the "ascent" pics and you decide if your models are doing their best for you.... 
On your three shots, I think they lack a little impact as on the two group shots you can't see anyone's eyes. The diver on the line could work better if you edit/crop out the hands at the top of the image - and see if you can lighten the diver's face so you can see his eyes - but there may be a bubble across his right eye (see what I mean about difficult?!). Could you get a bit of shadow detail using, say, Lightroom? There's a lot of "black".
On your single diver shot, you might try lowering the Brightness a bit to take some of the glare/reflection of the reflective tape on his dry suit and the octopus hose. And, sorry to say this, but pics of diving models in black masks, in my view, hardly ever work! The eyes just don't look right.
Sorry Terrriesrist, this is all a bit counsel of perfection. As I say, getting good pics of divers just isn't easy - especially in those conditions: cold, darkish, black dry suits, iffy viz/turbidity.
My experience is that if you don't go about "diver shots" in a fairly calculating, deliberate way, you generally end up with an image which is probably not what you are after. Try working with one "model" and explain what you are looking for before you start the dive. Then use some signals when you start shooting. Take LOTS of shots as you can bet your last pound that there will be closed eyes, bubbles over the mask, snot dribbling, fish in the way, weird looking ears etc etc. Multiple divers is a nightmare.
As for taping strobes etc, you get backscatter (forgive me, granny, if I'm teaching you too suck eggs), because you are lighting the particulant in the water that is between you and the subject. So you have to set the strobes in a way that they light the subject but not the water in a direct line between you and the subject. Taping would make no difference. So, for example, the shot of the diver on the line: you might try having the strobe at approx 45 degrees to the line between you and the diver - and as close to the driver as you can get it without, obviously, the strobe getting in to the image. This should reduce the backscatter - but, quite possibly, not eliminate it (You can use Lightroom to edit some of it out). Remember that the strobe will, realistically, only light a foot or so of the area it is aimed at. Quite often, especially at that relatively shallow depth, it may well be better to orientate the driver so that he is facing the sunlight and use ambient light to light him with the strobe then doing less of the work.
I hope this is of some help......
