Many cruise lines now have two single mixers, one for youngun's and one for mature adults. Even if you just sit and watch, at least go to the mixers. Now, I have a hard time thinking of myself of mature...old is okay, but mature?!?--horrifying.
But, cruises are an easy way to inch back into meeting people. You can chat with someone a bit, then agree to meet the next day for a light activity and not get into the old meat market mentally. Forget picking someone up, just chat with people. Almost everyone is friendly on board. After all, you're all on vacation and literally in the same boat! The first cruise after I got divorced was great for me. I found out that I could socialize without feeling pressured. Also, I recommend talking to everyone, not just singles. It takes away the pressure of the single "scene" mindset.