Another key bit of inspiration was seeing a clip of some of the fights in Dune 2. If you've seen it or read it, you'll know that a key part of the narrative world is that science magic and some hocus-pocus about worms means that nobody uses guns and most of the fighting is done hand-to-hand. It got me thinking that if a bunch of frog-women were to storm an undersea base, there'd be a convincing argument for all the fighting to be done with knives and spear-guns, so that stray bullets don't pierce the pressure-hull and cause the entire base to implode.
Here, you're looking at the initial concept renders for the opposing teams of divers, as they'll be dressed for the fighting in the tunnels and the domes once the attackers have breached the defences.