I agree with Mislav, two good buddy's are better than one, but finding the right trio can be challenging!
This really shouldn't be true, but I'm sure it is. Just a bit of training, or even just some experience diving in trios and a commitment to increased situational awareness, and you have a good team for basic recreational diving.
I'm lucky enough to dive within a community of people who are all trained this way, and we can put any three in the water and see it work well.