I had limited success useing "point at" but the hair wants to recede or otherwise looks foolish. If you're talented enough, you might be able to make your own underwater hair models using the information in a tutorial called "morph hair" or something like that. I think its in renderosity's poser tutorials. It uses the idea that you can change hair models by setting a parameter dial. Then you could make a series of hair models showing the changes you want, keyframe them and set the dial to change at certain points ... It could work? Sounds so complicated ... I wish I had the time and talent to do it.