Deep water

dude
Dude
DUDE
...
I have about a thousand things to say about this but one of them trumps the others: When you talked about the experimental drawing you were doing, I did NOT expect this. Like, at all ._. This is f***ing gorgeous! It's everything I love put together in one picture and it's so beautiful ;_; I might almost shed a tear or two. Purple sneklady = best sneklady <3

This picture in particular might be the reason why I love experimental drawings so much. Going against the expectation, the norm of what you've used to do, the given design of a character, a landscape, a building, whatever it may be, gives me a lot of satisfaction to see because it is something new and unexpected. I'm not saying that new is good just because it is new, but forcefully breaking one's habit on occasion can be a good thing for creativity and helps to round up a character. I mean, even if I have quite the arsenal of reference sheets by now, and I'm well into the story of TLH as of now, I still redesign and revamp not only scenes and the plot, but characters and entire settings as well. And judging from this fine snakelady here, I should say that experimenting has served you well here. There are a lot of new and invigorating aspects that I think bring out Scylla more out as a design.
First off, the most prevalent change, the tail. It is a big commitment to change something as integral as Scylla's tail is to her character, since it dictates how she moves and behaves and with it, pretty much tells the viewer what can be expected of her. A dolphin-like tail differs from a snakelike tail when association is concerned, no? While Scylla has always been *cough* not the purest of characters, her more fish-like appearance didn't play into that character trait but with this new snakelike appearance, the symbolism of a snake is associated with Scylla. That and I personally think snakes are elegant as sh*t, so on a personal level I am able to associate that quality with Scylla. All in all, it was a brave choice to change her tail and I think I agree with you: it is a keeper, for sure~!
The colour scheme is a whole another matter completely. It doesn't affect the symbolism and associated qualities as much, but it does hint a little towards the character itself. Previously Scylla had quite realistic yet at the same time mellow colour scheme (which is understandable, as not everything in nature can be coloured with all the colours of the god damn wind) but with this darker, more intimidating colour scheme she takes on a lot of colder colours which play for the overall feeling we get of her: she appears more cruel, calculating and conniving. I think you of all people can see why Jack has as many cold colours as he does, and the same applies here for Scylla. Personally I can say that I adore the colour scheme (especially the purple hair) but I wouldn't trust my opinion if you feel a bit unsure about it, since the main reason why I like these colours is that many of them happen to be my favourites, which makes me a bit biased about the colour scheme as a whole xD
I love what you've done with the details, as well. There are a lot of different variants of details, like the glistening light the hair reflects, the design of the cross-straps on her chest or the scales on her tail. All of them work a little different angles into the character, and all of them work, in my opinion. I like how the hair glistens, I would imagine Scylla of all people appreciating things that sparkle and glitter the way her hair does (as is evident from her apparent affection for jewellery, i.e. I see you there, you lovely earring <3), and it brings more to her character as a whole. The scales on her tail work towards the snakelike appearance so they have quite the practical use but the cross-straps she has are an interesting - and new - addition to her design. Personally I feel they bring somewhat of an elegant dash to her outlook, moreso than the Godiva hair she used to sport before.
As far as I am concerned, the cross-straps are a keeper as well, but if I am to nitpick about SOMETHING about this, so that you might possibly even learn something from my utterly useless wall of praise, I must say that if you're going to keep the cross-straps, let them circle around to her back from the waist. Should the cross-straps be cloth, what I suspect them to be, such an angular turn right under the breasts would only result in them falling off, since boobs aren't that much of a muscle. If the straps go all the way down to her waist and wrap around there, they would be able to stay on her chest. Either that or you run a third strip right under her breasts and attach the two previous straps to it, so there's something pulling them down because as they are now, there's nothing keeping the straps in place.
Other than that, you've done really wonderful work here! I love the fresh look you gave Scylla, and I may even go so far as to say that this is my current favourite iteration of her design~