I agree with Bubbletrouble. I attach a discussion of the issue that is quoted from my book, co-written with my wife Debbie, "The Scuba Snobs' Guide to Diving Etiquette" available on amazon.com or barnesandnoble.com in paperback or as an e-book.
LOOK AT YOUR GAUGES REGULARLY
Ok divers, listen up. Before we go on our next dive, let’s review some basics. Running off of your first stage (that thing connected to your tank of compressed air) there are four hoses. One is a low pressure inflater hose attached to your buoyancy vest. The second hose goes to your primary regulator so you can breathe under water. The third goes to your alternate air source (unless you have a low pressure inflater alternate air source set up) so someone else can breathe off your tank in an emergency. Finally, the fourth hose goes to your submersible pressure gauge and maybe to your computer, what we will call your “console.” That is what we are talking about here, the gauge console at the end of the fourth hose. ( We get it- some of you have wrist mounted integrated, no hose computers and stuff- fine. Quit interrupting).
As to the stuff at the end of the fourth hose, (or on your wrist mount) look at it now and then! Some people never look at their gauges, believe it or not. You should look at your gauges before your dive and see if you have sufficient air for the dive. You can look at it during the dive and you will see how much air you have left. Isn’t that something? Look at your computer or gauge during the dive and it will tell you how deep you are. Look at your computer and you will actually see how much no decompression time you have left at the depth you are at! No joke! It’s amazing! So please, look at your gauges!
Why watch your gauges? For your safety and the safety of those around you. We all want to enjoy the dive, and we want you to enjoy the dive too. If your air is limited, please consider reducing your depth by ten feet or so you won’t make us all go up because you are low on air. To know where you stand on air, or how deep your are, YOU NEED TO LOOK AT YOUR CONSOLE! It’s part of good diving etiquette. Doing so will help reduce the times other divers have to retrieve you from unsafe depths, or escort you to the dive boat as you suck the air from our tank (which we will share willingly if needed ) because you didn’t pay attention to your air supply. Keeping an eye on your gauges will also enhance you awareness generally, which leads to better diving skills.
We shudder when we hear a diver after a dive ask “How deep did we go?” or “How long were we down?” Sometimes they will look at their computer for the first time after the dive and say “WOW, I didn’t know I went that deep!” These people are disasters waiting to happen. A distressed diver can be a hazard to those who try to assist them. Be a safe diver. Be aware. Look at your #%!**+ gauges! Read them often. Live to dive another day.
