Yes, actually. I am. I found this site while researching information about death/suicide while scuba diving. My two biggest considerations are 1) i need to make my death look like an accident because I wish to spare as much as possible the additional trauma my 11 year old (today!) daughter will experience if she were to know that my death was suicide. 2) I want a method that is as painless as possible. What I learned in searching death by scuba is that there's not much hope for dying that way that won't be painful and distressing. Then I came across in this site what's known as the Shallow Water Blackout (SWB) method. This method has been discussed at some length on a few different threads here so I encourage you to search SWB here so you can catch up on what's been discussed. In short, the method involves several minutes of intentionally hyperventilating so as to (if I remember correctly) raise the level of CO2 in your system. Once you've completed the hyperventilation step (and there's debate/discussion here on how long that might actually take for any given person, but let's just say about 5-7 minutes or so) you enter the water (bathtub, pool, lake, whatever) and submerse yourself while holding your breath for as long as you can. The idea is that if you have adequately raised the level of CO2 in your system from hyperventilating, holding your breath under water will lead to a black out rather than the forced breath you would normally experience in the absence of elevated levels of C02. Because you are under water, when you black out you will either unconsciously take a breath and thus drown or you will simply die from the brain's lack of oxygen. So the selling points, for me at least, are 1) that it seems to be a fairly simple method, 2) it should look accidental (though my family knows I'm a diver and a former lifeguard from years ago so they may in fact entertain a suspicion or two that it might not have been an accident - they're fully aware of my life circumstances, which were nothing less that a complete fucking collapse of what had been a beautiful life so I cam imagine them wondering at some level if I intentionally ctb) and 3) if it works as described it should be relatively free of pain and distress. That said, there are others here who clearly do not feel as I do about SWB. I've discussed this with them and heard their reservations and I think you should take the time to read through the relevant threads to get multiple view points. Just search SWB here. You will find, I believe, at least one thread dedicated to SWB that is pretty long and contains links to outside sources of information. One source I have found that you might check out is something of a memorial to about 30 people who have died from SWB - these weren't, as far as anyone can tell, suicides. But it does clearly indicate that the experience of an underwater blackout can be fatal in a matter of minutes.
http://www.shallowwaterblackoutprevention.org/survivors/
Hope you found this useful.