Sorry...had to split for awhile and didn't really address your question. I was an IV drug user for many years, and though there were times, when coming off a coke binge, when I was ready to shoot ice water, it was never a practice I pursued. Claiming that shooting water reduces anxiety sounds (to be blunt) like a bogus explanation of a desperate user. I can see doing it once, but what would be the reward? Many of develop a sort of "needle fixation", but we used the needles for a reason: the rush.
To give the guy the complete benefit of a doubt, shooting water is a terrible way to address anxiety. The fact that he missed and messed up his wrists is further evidence that the guy most definitely has a problem. Having other people discover my IV use was one of the most humiliating experiences of my life, and I lied with impunity to rationalize or conceal what I was doing. Viewing IV drug use as anything less than a desperate and despicable act, and an indication that the users is in desperate need of help will only prolong the disease and set the addict up for horrible consequences. The guy needs immediate intervention!