It seems like you are imagining. If this is so then noting it, "imagining, imagining" can be very helpful. It's probably just a restless mind trying to entertain itself. Perhaps beneath it there may be desire because when we get bored, we may want to create stories to entertain ourselves. Oftentimes in our normal life that's what we call daydreaming. Because we are bored we create stories and fantasies. So "imagining, imagining", "fantasy, fantasy", etc.
Or else if it is just bubbles, treat it like bubbles. Watch its impermanence if it's just bubbles floating by, but try not to get lost in the bubbles. It's a bit like another analogy I use, where you are standing at a railway crossing and you are just watching the train go by with the different carts. That's fine, just watch it go by, there's no problem. However when we jump in the cart and go down the track a little, we have gone too far. So we have to jump out and get back, and just watch it go by again. Because you don't know where that train is going and we would like to get on a train where we know the destination, rather than just get on any train, right?