I might as well start with an apology that these pictures surely aren't that inspiring. Photographing bubbles in a bad light turned out to be quite difficult, and definitely required more patience than I had at that moment (there was a hot bath waiting for me, so naturally my patience was even less than usual).
A while back we went to one of those smaller supermarkets, where they sell food and occasional "good deals". I am not sure what an international equivalent would be, but I am sure the same concept exists all over the world. There are all those usual groceries, and then there are an aisle or two filled with other things - usually tools, home decoration, socks or similar.
We found this little funny thing that is a mat that you place on the bottom of the tub, which will kind of turn the tub into a jacuzzi. Since it wasn't very expensive we decided to try it and it actually works really well, creating a lot of bubbles. One doesn't really feel the mat-thing in the bottom, and the only drawback (except that it isn't exactly beautiful) is that the water turns cold faster.
Here are my not-so-successful photos of the bubbles. We will, eventually, replace the tub with a real jacuzzi-bath, but it's a bit further down the list of everything we want to do. After all, the tub works fine and it was a real bargain because I got it on the equivalent of craigslist for just a box of chocolate.