Sorry to hear your trip was a washout. My wife and I only left Okinawa last August, after 15 months living there, and miss it tremendously, especially the diving! I hate to tell you that you've missed a great experience but...

At the very least, don't miss going to Churaumi Aquarium, it's definitely worth a visit if you havn't already done so; and if you're staying in the Motubu peninsula look out Pizza Kaijinho (Gaijin call it Pizza-in-the-sky), it's a delightful Okinawan pizza restaurant in the hills with a stunning view over the bay. It's a bit hard to find, give them a call first: 098 0475537

Once again, commiserations about the diving, I know what you're missing.