Some really great tips here!
And of course, big thumbs up for the whole site. I am not a regular poster, but tend to read a lot of very useful stuff here!
Would like to add some of my experience:
I read somewhere, that the model should avoid washing their hair and using conditioner - clean hair tend to catch a lot of small air bubbles. I tried some of the shots and it turned out as a great tip.
Try to aim for slow fluid motion of the model, with short stops and direction changes, so it animates the hair and the dress.
When choosing a poll for the shoot, try to find one with clean water. We booked the night, and started shooting around 0100 hours, to give time for the water to settle down. (that is, if you don't get a private pool
some of the images can be found here http://www.flickr.com/photos/40503675@N03/6654661997/
On the shots we used 20mm lens on full frame camera. The light was the available pool light, that we could point towards the surface and use a deflector. On this link you can find some BTS shots - http://www.pleinsud.com/news/