Your Tidebreak study is extraordinary and a surprising inside in mermaid anatomy. We are kinda used of seeing mermaids as very delicate, colorful beauties, especially when you think of the "Original Wavedancers". You show us another type of beauty - strong and muscular, monochrome and bald - adepted not to our romatic imaginations, but to her deep sea environment.
The human upper shows body clear defined muscles ... balanced between "typical" male and female. The muscles of the tails look interesting ... and alien. Have you based in on whale or fish studies? The back fin was a surprise for me - I wasn't aware she has one.
Do you consider a variant tirnaround, showing her bioluminescence?
Must admit that I wish to see a drawing of her in movement - true to your specifications.