As I have been diving for many years I have had the opportunity to observe many types of divers as buddy companions. For many years I was used as a buddy for new divers in Jervis Bay in Australia where I dived for 20 years.
I have a basic list that I want in a buddy:
1. Someone who will do a sensible gear check.
2. A diver who keeps me informed and will watch what I am indicating underwater.
3. A diver who respects the 'Stop, Think and Act' maxim if something goes wrong.
4. Someone who will be where you expect them to be and agreed to before the dive.
5. A diver who is capable of looking after themselves.
These are my 5 'great if you can do this' points. On top of this I like a certain humility and respect for the dangers involved in what we are doing. Overconfidence leaves me worried about a buddy, particularly when their underwater skills dont match the pre dive talk.
[6] A diver who can see stuff underwater would be great but these are few and far between in my world.
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This is a great question, which I wonder about everytime a boat captain asks me to take on a single diver as a new buddy. Therefore I keep the "list" as short as possible.
When we start, I tell him/her how I will share air/nitrox if needed by donating my primary.
Then I tell her/him my handsignal for "what is your SPG pressure?" The sign is made by pointing to your left palm with your right index finger and tapping it 3 times. They are free to count off numbers or else to show me their gauge.
Then I tell him/her the signal for turning around and heading back to the boat. The sign is made by pointing to your left palm with your right index finger, then making a circle in the air with your right index finger, then pointing your thumb twice over your shoulder back behind you. It represents that "we have reached our turn-around SPG pressure, time to turn around, head back to the boat."
Finally I discuss the lost buddy procedure, which should never happen, since I normally have my DPV with me, therefore there is no way she/he can swim away or outrun my DPV, because I always watch her/him very closely. At any rate, the lost buddy procedure is to retrace your steps for 1 minute, shining your light in a circle (if they have a light), then ascend to 1/2 MOD for a 1 min safety stop, then to 15 ft for a 3 min safety stop, shining their light the whole time in a circle, then meet up on the surface before swimming back to the boat. If 15 mins passes on the surface, then swim back to the boat alone.
I do not do gear checks, since I feel this is the responsibility of each diver on his own. However I will ask "is your air on?" Although I won't touch his/her gear, unless they ask me to.
Other than the above, the only signals I will use underwater are to point, if something is extraordinary, or to signal OK, or to nod "yes."
You will never know if someone is going to stop, breathe, think, and act. I have dived with divers who have tried to swim away, who have run OOA, and who have tried to bolt to the surface. Trying to bolt to the surface is the only thing that really worries me, so those I have restrained and helped them to calm down underwater, after which they have always thanked me back on shore.
I have learned that divers are rarely "where you want them to be." Therefore best to watch them carefully and stay close. A DPV makes this very easy to do, even if the other starts swimming away furiously after a mermaid or some beautiful fish.
If a boat captain askes me to buddy with another separate diver, it is obvious the captain wants me to watch over her/him. Otherwise we would both be diving solo at the captain's pleasure.
If you are an instructor or a D/M you should be able to cope with anyone as a buddy.
Therefore I suggest that everyone strive to become a D/M as soon as possible, at least.
