I was also very lucky to have the lovely Chelsea to work with. I think the shot on the decking (above) is very Hollywood!
Whilst the clouds made it easier to shoot (like having a huge softbox) it was quite chilly at times, but that wasn't going to stop Chelsea getting in the pool...
All of these shots are lit using a mixture of ambient and off-camera flash.
For this set I used a Canon 580EX-II in a Lastolite EzyBox. The camera was in Manual mode at all times, but the flash was fired via a second 580EX-II in the hot-shoe using E-TTL metering.
Using a little negative compensation the light from the flash blends in nicely with the ambient giving a much more natural feel. I think it worked very well.