Thanks to all for the feedback and suggestions about my Gatsby Summer Afternoon dress fabric dilemma! The general consensus was that navy and white would be adorable and that the floral fabric was worth salvaging. I decided to get over my issue that it wasn't "nautical" enough and just go with the blue floral voile.
Here's a look at my current progress on the bodice. I quickly constructed that flower as a prototype with some navy lining I had lying around. It's simply tacked on with a pin. The same lining was used to make some bias trim that is bordering the neckline. That, too, is tacked on the dress form with a pin. I do believe that's a good look but am open to opinions.
Ignore the peplum and back cascades, those are also just pinned to give an idea what it will look like. I've already finished the underdress and only have to sew the cascades onto the back. Thankfully, I should be done with this dress by the weekend and will be able to move on to the Gatsby dress for my sister-in-law.