I made a couple tests for you, using a simple stabilizing method. You just pick a point that's consistent across all the frames, and align that point in each frame to the same place. I did this in Photoshop just using a couple guides to line up each frame real quick. On one of them, I chose to align to a bright point in the BG, that light right behind the first 'e' in your watermark. On the other, I aligned it to the top of the pendant. Both of them, I cropped the frame range, so they're shorter.
Unfortunately there's some change in where the pendant is, in relation to the background. It 'drifts' a bit. This is called parallax. It means that this gif would be a little tougher to seamlessly loop without some heavier-duty work, that's all. That's why you still notice a jump in both when the loop starts over again. Also, since the original watermark was still, now you notice it jumps around because of the stabilization I added, heh!
If you wanted to get a seamless loop, make sure the camera and the pendant are held stationary while you blow the bubbles. This will make it a lot easier from the start if you want to do a nice seamless loop without too much effort in Photoshop.
*Actually, in the interest of accuracy, the pendant drifting isn't true parallax, as that is caused more by camera movement. Here, the parallax effect is more from the pendant's movement, than from the small camera movement.