If that's in water and those are bubbles of air, I wonder exactly what is propelling them. They aren't all moving in the same direction, so it's hard to imagine that it could be buoyancy.

As for the one that appears to speed up, it also appears to be coming toward the camera. If thats the case, then its upward motion would appear to be speeding up in the image - if you get closer to a camera, then the same amount of lateral motion will result in a greater change in the angle between the object and the camera. (On the other hand, if the object really were accelerating straight up then we'd expect it to trace a parabolic trajectory, not the straight one seen in the video.)