Okay wow orz sorry this is going to be the first critique I've done in a long time! I'm not really good at critiquing, and I'm rather nervous to do so, so I hope this helps! I'm going to apologize like 10x after this sorry!! This critique is going to be so over the place omg

First off, this picture really stood out to me, because of its cool tones you used, and of course the drawing altogether, but there is somethings I think are rather off. Sephora's expression is like I love her grin, her outfit aaaa ;w; and I see that you also did some changes to her appearance (quills? please correct me if I am wrong)

The pose is great, but there is some things rather off that I can see. First off, would be how the arms are. The arm hiding behind the head seems to be longer than the one hiding behind her waist. Same as the hands. The "Peace" sign fingers, the index is taller than the middle, and that hand is more large than the other one.
The breasts also don't work that way in that bathing suit unless it is suppose to add some oomph. They are lower down, and aren't that perky.
For the legs, they're nice the only thing that I think is wrong, unless you prove me otherwise (I'm bad at critiquing so my apologies!) would that, wouldn't the left leg (our right) be overlapping the swimsuit or???
On to the swimsuit, this part I am not 100% sure on but with that pose wouldn't there be some creases happening,

For the shading, it really confused me, you got the light source down, but it seems to transition from soft to hard back to soft again on areas. The shading on the hind quills/hair seems to me very inconsistent with all those extra lines, but it adds more detail and it does look nice. I like the cooler more blue tones you used for the shading it matches the background.

For the background itself, it can use some work at first I couldn't see the clouds in the sky, and the moons ray/glow isn't that linear to the waterfront/water-body on such a clear sky to my knowledge, if it was a cloudy night sky then it could be more linear, and direct in one area. The water, I'm wondering, wouldn't it be darker at night. The background island/beach the only thing I can point out that there is a problem would be that the fires too big (unless its a big campfire), and too solid for the distance it is at(? I don't know what word to use here so once again my apologies) it would have a glow, and the flames colour wouldn't be that red.

For the lineart, its nice, crisp and clean. But where you put the highlights it seems to have some differing and more "noise"(pixels???) to it, I'm not sure how to explain it correctly but hopefully I got the point across.

The whole picture itself is a huge improvement from what I've seen of your art! You really show that you do know your stuff, and this beach picture is really nice, same as the theme. Looking back at your old beach/other pictures you did previously back in 2012, and also early 2013. All I have to say is keep on trucking because you got it! References, Tutorials, and Just doing art, and what you're doing will help, and they have from what I've seen. Keep up the good work!!!