In this case if the diver really knew there was no hope then no this wasn't a chicken's way out. But it should be noted that drowning would've been less physically painful than dying of a stab wound. It's still understandable as doing it that way would've given him more control over how he died. I wouldn't have done it as I would've wanted some small hope of being rescued, but in cases like that it's your call.
In most cases though yes it's a chicken's way out. Even if you are depressed that doesn't mean you can't go on living, it doesn't mean you should just quit. If you are depressed, get help, don't commit suicide.
People who try to say that suicide is not cowardly think they are being compassionate, but what you are doing is legitimizing and hence encouraging suicide. We should instead emphasize that suicide in most cases (except cases like in this article and cases of terminal illness) is a terrible decision to make in many ways (selfish, foolish, and cowardly being among them), but that suicidal thoughts or feelings or even attempts do not mean the person is terrible (an attempt is a terrible thing to do but it does not mean the person is terrible). Suicidal people should be encouraged to get help so they will not be suicidal anymore, NOT validated in being suicidal.
Most people that commit suicide cannot stand the pain of living. Life is very painful and it takes a very strong willed person to get through it. The only exception to this is when you know you are beaten and you are already looking death in the face and you want to end it on your own terms and you don't want to be ruled by your sickness or circumstances.
I cannot imagine the amount of pain and suffering a person must be enduring to choose to end his life. In no way and under no circumstances, should suicide be ever considered easy or a coward's choice. As humans, we can strive to be better than that and we should try to do all we can to help these people who needed help. I wonder if a selfless rescue worker could have beaten the odds and rescued that poor diver in time, but we will never know for sure.
The particular case of the scuba diver may have been an act of desperation as he faced death by drowning. I think the human spirit fights to survive under the worst of odds so the act of suicide is not a chicken's way out. Suicide is usually considered as a last resort.
Suicide is not undertaken by "chickens." It is usually done by those that have severe depression. This can be caused by a multitude of mental and physical factors. There are also suicides done by those that are terminally ill. These people do not have any fight left in them, and are seeking to ease their physical pain.