In Greek mythology, the Nereids (neer'-ee-eds) are sea nymphs, the fifty daughters of Nereus and Doris. They often accompany Poseidon and are always friendly and helpful towards sailors fighting perilous storms. They are particularly associated with the Aegean Sea, where they dwelt with their father in the depths within a silvery cave. The most notable of them are Thetis, wife of Peleus and mother of Achilles; Amphitrite, wife of Poseidon; and Galatea, love of the Cyclops Polyphemus.

more information here:
http://en.wikipedia.org/wiki/Nereids

here tou can see the steps:
http://www.flickr.com/photos/maril1/2759531223/

for this work i working in the photoshop Cs2 with the simple paintbrushes and with wacom bamboo fun.