Note: Non-DIR answer ahead...
In this case -- I'd go at it alone. Depending on the dive I probably wouldn't even bring a pony bottle.
I've done dives similar to this but not quite. Awhile back I went on a meg-tooth hunt dive off the coast with a buddy of mine. This was our first dive together, although we were both trained the same at school so we were very buddy conscious.
The dive was in September so the water of the NC coast was quite warm -- upper 70s if I recall, maybe even low 80s. 110ft to the bottom, and we could see the bottom when we splashed (plus columns of silt people were stirring up looking for fossils).
We dove as a loose team. We were within 10ft of each other the whole time on both dives, but we were concentrating on the hunt. The goal of the dive was fossil hunting, and not site-seeing. We were close enough to help each other quickly if needed, but we weren't crowding each other. But we weren't paying nearly as much attention to each other as we normally would.
Most of the people on the boat were 100% alone, which is fine with me. I can't really imagine fossil hunting as a 'team' dive, to be entirely honest.
I suppose the point of my story is that not every dive can be accomplished as a DIR-style team dive, but there are still plenty of dives where you can be safe while going at it alone.
While I do generally subscribe to the DIR team philosophy, I also subscribe to the "you need to know how to take care of yourself" philosophy, as well.
A large majority of my dives are team-oriented, but many aren't. If I am escorting students at the quarry, while I should be able to count on them to help if there is an emergency I'm not going to count on it. They are task-loaded on their first dives, and I swim above them. Most of the time they don't know I'm there. That certainly isn't a team-oriented dive; thus, I have to be completely self sufficient while escorting students.
