From the Disney Park Blog:

We are just a couple of months away from the official opening of The Little Mermaid ~ Ariel’s Undersea Adventure at Disney California Adventure park. Walt Disney Imagineers are working hard to make sure you feel transported into Ariel’s world through every detail – the water, the fish, the hair….yes, the hair! Ariel’s hair posed a particular challenge for Imagineers, one they hadn’t encountered before – how do you make hair that’s technically out of the water look like it’s floating underwater? Take a look at their progress.