I think that, unless you dive with the same buddy and practice emergency procedures with that buddy a lot, then you are actually diving solo. When you are buddied with someone you have just met on the dive boat, it is unlikely the two of you could rescue each other, rather would more likely make an urgent situation worse. I dive solo a lot, in california, but I don’t dive very deep, nor penetrate overhead environments. It’s all about recognizing and managing known risks. If I decide to learn wreck penetration diving, or cave diving, I think I would have to find a buddy that I could practice with a lot, and keep practicing with.