I realize that none of this may be ideal, but unfortunately I have a time limitation as I will only be in La Paz for 3 days. I've done quite a bit of searching (I can use Google well, etc.), but I haven't really found a clear answer to my question.
Since I will be so close, I'd really like to see Lake Titicaca. It's fascinated me (maybe the name, maybe its reputation as the highest navigable lake) since elementary school. It may seem silly to some, but at this point, I'd just be happy to have seen it in person. So my question is this: what's the easiest way to see it in a day trip from La Paz?
I realize that there are overnight tours to Copacabana/Isla del Sol. I'd do this if I had more time. I already have accommodation in La Paz, so this is not a viable option this time around at least. I've read that there are minibuses (or vans?) to Copacabana leaving from near the cemetery in La Paz. It's unclear to me whether or not this is viable option for a day trip. The tour company websites (that I've seen) don't list one-day tours from La Paz. I don't know if there are tour possibilities not listed online. I don't need to be wined, dined, and entertained. I don't need a hike on Isla del Sol. I don't need to even go all the way to Copacabana if I don't have to.
Has anyone here gone to the lake from La Paz in a day trip? If so, how? Or does anyone have specific suggestions re: how it could be done? Or if you really think it's just not viable, that would be helpful too.
Thanks in advance for your time!

