Things you'll need:
* light, medium and dark blue nail polish (I used Barry M in Cobalt, Blueberry and Blackberry.)
* wavy scissors
* top coat
1 - Apply your medium blue nail polish. Allow it to dry completely.
2 - Cut a piece of tape with your wavy scissors and place the tape on the middle of your nail.
3 - Paint the nail on the both sides of the tape: with lighter blue polish on one and darker on the other side. Take the tweezers and carefully remove the tape while the polish is still wet.
4 - Repeat on other nails, clean-up with a brush dipped in acetone/nail polish remover and apply top coat.
Simple as that. =) BTW: I can't wait to see the sea again.
Thanks for looking and commenting!