CORAL

Dr Bradshaw hadn’t always had scales. I was struggling to get used to them. Here, as he snaked across the lab floor beneath fluorescent lighting, they flashed like the bottoms of brass pans. As if in response, my flesh crawled with goosebumps, almost becoming scaly itself. The sound of thick plates sliding over smooth concrete trilled as beads over marble might, and that such an elegant noise came from so deadly a creation only made my skin crawl further. It seethed.

‘Isn’t she beautiful?’ the doctor asked, watching the whale pirouette in its cubic home. ‘And her payload . . . ’

My hands were pressed tight to the glass, separated only by a layer of sweat. Adrenaline pummelled my temples; I found it hard to breathe.

Just line-edits, really:

• 'they flashed like the bottoms of brass pans' - I'd find a better simile.
• 'As if in response, my flesh crawled with goosebumps, almost becoming scaly itself' - why not just simply have her say 'they made my flesh crawl'. It's more direct, and I think more effective for the brevity. Plus, I don't think goosebumps can feel like scales, either.
• 'The sound of thick plates sliding over smooth concrete trilled as beads over marble might, and that such an elegant noise came from so deadly a creation only made my skin crawl further' - firstly, look at your similes again. Why have you chosen to compare it to beads? Beads are not unpleasant. If, however, you'd said something like 'the sound of plates... grated on me like the sound of fingernails down a blackboard', then you'd be likening the sound to something unpleasant, which would add to the idea that your POV character doesn't like the scales. Secondly, you're repeating yourself - we already know that the scales make her skin crawl, so why labour the point? Lastly, I agree with annepin that the scales would scrape, not trill (and I'm not sure beads would trill, either. If they were glass beads, they would 'tinkle'. Otherwise, I'm sure there are other words).
• 'It seethed' - her skin seethed? That's a pretty violent image - I think it's a little excessive.
  

Here's my example (please excuse the rubbish knife simile - I'm not suggesting you use it, but it'll do in a pinch to demonstrate what I mean about choosing similes for a reason):

'Dr Bradshaw hadn’t always had scales. I was struggling to get used to them. Here, as he snaked across the lab floor beneath fluorescent lighting, they flashed like knives. They made my skin crawl. Thick plates scraping over smooth concrete set my teeth on edge, like the sound of fingernails down a blackboard. I winced.'

Sorry to rewrite your work, I'm just trying to show you what I'm getting at.

Anyway, no problems after 'It seethed', though your POV character seems to get very panicky all of a sudden - I'd tone down the 'Adrenaline pumped my temples' sentence.

All that said, I'd still read on - I'm intrigued.

Hope this helped .

Daniel.

And I'm still not sure about the "deadly creation" referred to in para. 1. Seems to be Dr. Bradshaw, but I'm having a hard time with that out of context. And whose claws? The doctor's? Martin's? (I realize that this all may very well be explained in the next unseen line or two...)