Look at the modelling on your close-up shots, like the eyes of the crocodile fish (my favourite image in your set). What has happened is that the angle between the strobe and the subject is greatest when you are close, and this introduces some texture. A larger angle (the strobe position farther away from the camera, vertically or to either side) would exaggerate the modelling shadows, and spoil a close-up, but perhaps improve an image taken from further away.
Inons are not the most powerful of strobes and need to be aimed at the subject, particularly at a distance of 1m. Much further than 1m and the light isn't very bright. Closer in, particularly when you get down to 40cm or less edge (or "Edge", after Martin Edge) lighting can work well, with the strobe angled away from the subject so that only the outer part of the beam illuminates it.
Needless to say Martin's book has a detailed explanation and examples.
Of course, the temptation is to go to two strobes, but you're getting nice lighting from one, so I recommend to keep experimenting: try several frames of a cooperative subject and vary the strobe position. It's a pity that Inon have dropped the aiming laser, which used to help me point the strobe in the right direction.
Tim
