I've been thinking about everything you've all said and I think you may be right that the Moroccan Oil isn't as moisturising as I thought. It was fine before I started swimming, but I do need more moisture now.
I'm going to pull out the very light, 'cone-free conditioner I used in my CG days and see how that does under the MO. If that works I might try with my heavier conditioner too
Thanks for the ideas!