Can I use a GAN to increase my Dataset used for Image detection?
In short: no

If you don't have enough images now then you almost certainly dont have enough to successfully train a GAN (it takes more than you think). If you can't train a GAN to reproduce good images, then you don't have images that are going to give you high accuracy for your YOLO effort. The most likely scenario is that you would end up with an algorithm that is really, really good at detecting GAN images that looking nothing like your side scan sonar validation data :)