These are the basic hand signals that I have seen actively in use in the Chicagoland area. You should always work these out with any new to you dive buddy before you splash. The first group are "the basics". The second group are useful for recreational team diving, particularly in the local quarries.
OK
This is both a question and a response. If someone flashes you the "ok" you should pause....yes pause...think about the question...and then respond back with "ok". Simply flashing "ok" back is not what the signal implies. It is a genuine question.
Problem
Generally you then point to whatever is the problem....like your ears (equalization).
Stop
Hopefully this one is obvious
Ascend or End The Dive
ANY one can end a dive at ANY time for ANY reason
Air Pressure Check
Most of us learned the "two handed" version. So the one handed version could be confusing as it looks like a "come here" motion. The "come here" motion is actually a more exagerated version of this with the open hand instead of closing to a fist.
1,700 PSI
I prefer using the arm method for indicating pressure as it is easier to see and understand (for me) than flashing a bunch of fingers. Place the fingers across your arm meaning "thousands" and then show the next 100's number. It only takes 2 motions instead of 4.
Low Air
I'm low on air...no screwing around...we need to get to the surface but it is not an emergency
Out of Air
This should be a VERY obvious motion. Not some tiny thing with your fingers....get your entire arm into the motion. Make it obvious!Useful when Recreational Team Diving
Hold
Like stop...but to mean "hold position - don't move". So if you need to go check something or do not want your dive buddy following you...it would be better to give the "hold" signal instead of the "stop" signal. You then "hold" the position until the person who gave the signal gives a new command.
Turn The Dive
We need to start heading back to our exit point for whatever reason
Direction
Usually left or right. Do not show your thumb! That could mean you want to ascend or call the dive so do not confuse your buddy.
Level Off or Platform
Level off makes sense and is obvious....platform not so much. There are platforms in every quarry in Chicagoland and no generally accepted hand signal for it. So I've seen folks use this signal to mean "platform". Like saying "Hold, Platform, 2"
Question
Generally meaning you have a question for the person you signal that to. Like "Where is platform 2?" with the signal "Question, Platform, 2".
Yes / No
No is obvious. Yes will be new to most people.
Switch Places
Usually for when either you want to lead or you want the other person to lead during the dive
Kick Your Legs or Lets Go
As in...let's go that way. Or get a move on. During training it may have been used for "Stop Kicking Your Legs" instead.
Slow Down
I saw this one A LOT in my training!
Deploy SMB
You should know how to do this. If not...let's buddy up and practice.