SeaSecret and Hydrochic, but now there are a few more companies around. All offer great modest swimsuits in an array of styles, colors, and prices.
For your convenience, I went through a huge list of "modest swim suit" sites, and excluded the ones that just don't work for the level of modesty required of religious Jews.
Here are the links to some of the sites I found, my impressions of their offerings, and the prices you should find on the sites. I have focused on women's suits, but most of these companies also have children's suits, and some also feature boys and men's suits.
I have included pictures when they met the modesty requirements of my page (i.e. no women in revealing clothes that plunge or show upper arms or thighs.)
The prices are not out-of-line for quality swimwear--from $80-$150--and they include matching swim-ready headcoverings--which is an extra plus.
These are nice outfits, but don't expect the same one-piece design you see with Sea Secret. These are two piece ensembles, where you need to choose the top and skirt separately. They are very cute styles, though, and the two-piece idea is very nice--especially if your top half and your bottom half are not necessarily in proportion.
Another nice aspect of Hydro Chic is that their website is very easy to navigate, with a whole section of "short sleeve," and "3/4 length" sleeve styles, along with long and short swim skirts, shorts, and skorts. Prices are $70-90 for each piece.
Princess Modest Swimwear
A whole different take on the modest swimwear idea can be seen at one of the newer (to me, at least) sites: Princess.
These suits come in three and four piece sets of loose garments over tops and leotards. If you are looking for a swimsuit that is not as form-fitting, these are a good choice. Also, you will find some extra-large sizes on this site as well--which is very nice.
They also have a section of swim skirts and tops, if you like the more form-fitting suit. They also have a great selection of head coverings that are sold seperately.
Prices range from $90-$130.
The swimsuit pictured is only $65, and is available in a stunning array of sizes.
The downside of Aqua, I have to say, is that the website is very difficult to navigate. Look for the modest suits in the "cover up" section, and, if you have men in the home, don't go through this site with them present, as there are many revealing (by our standards) suits and photos on the site.
Prices Range from $65-$120.
Undercover Waterwear (UCWW)
Although the swim dress styles are similar, you can find a host of different colors and combinations on the site. Unfortunately, sizes only go to 2X.
Prices range from $50-$70.