Important Tips
These are tips from stitchers who have completed Mermaid or who are currently stitching this design.
...Tip for stitching the sky from Debi...
The sky is a combination of whole and half stitches, and one thing that's helped make the sky stitch up faster is doing the whole and halves of the same color at once. I made a list of all the symbols (from the leaflet) used in the sky, and noticed there were at least nine whole/half pairs:

\ and + (ecru)

// and the arch symbol (3774)

circled X and W (415)

division symbol and AE (415+928)

Q and lowercase phi (318+415)

4 and the = with the vertical bar through the middle (225)

/ with the veritcal bar through the middle and the three dots in an upside down triange (3770)

- and unslanted lowecase mu (762+928)

arrow pointing northeast and slanted lowercase mu (415+3752)


Notice there is a slanted and unslanted lowercase mu which are very easy to confuse. The mu basically looks like a fancy cursive "u". Don't confuse the \ and /, either, especially where they are mixed together.  These symbols are from the leaflet and I don't know if they differ in the kit version of the chart and the magazine versions.
NOTE: all half stitches are to be stitched in this direction: \

...A note about the border from Blaze...
Just trying to keep you guys from making the same mistake I did.
In the border there is a right side up triangle (932) and an upside down triangle (422+3782), and I accidentally did both symbols in the same color!!! Luckily I happened to look closely at the chart and didn't have to frog too much (aka rip out the color and start over), but just to save you guys the same irritation as me I thought I'd mention it!
P.S. from Prinncess: This is not as easy to avoid as it may seem...I found myself in danger of doing the same thing, so heed Blaze's sage advice and pay attention to those border triangles!!
...Anchor Marlitt vs. DMC Rayon...
The Anchor Marlitt is a very slippery rayon and can be easily replaced with DMC rayon (albiet, another slippery rayon!). The DMC, however, seems to be more readily available to most stitchers. Another substite for the Marlitt is Eterna silk, which is not quite as shimmery, but it has a soft matte sheen and is far easier to use.

Substitutes for the Marlitt 1034 Ecru:

DMC Rayon 30712 Ecru

Eterna Silk 10 Ecru

HOME
...to sparklie-fy the shells by Prinncess...
To really give the shells in the border some sparkle, I added the following colors: Sulky Sliver Thread 8040 Opalescent to the entire shells and backstitched the shells and spokes with Glissen Gloss Rainbow Blending Thread 618 Purple Red.