This is really cool. I think the composition is fine. You could improve/accentuate the narrative by adding a colour variation (red glow?) around the dome just left and below the female simmers head - it would add empahsis to the divers need to swim in that direction.
Love the mood and the whole setting. The sense of depth is very strong and as a result this one really pulls you in and makes you feel you're swimming there along with them. So I don't really know what you're talking about