OK, not an aquatic animal, but...When damselfly's go under the water's surface to lay eggs, they trap an air bubble around them to breathe.
A water bubble is made of air. If you remove the air from it it will not be a bubble anymore.
The level contains a bubble of air.
To prevent injecting an air bubble into your blood, which can kill you.
The Incas invented the bubble. back then soil was dumped into a vat and the air forced a bubble threw threw air.
The speed in which an air bubble will travel upwards in water will depend on how small the bubble is and the elevation in which the bubble is being released. The smaller the bubble, the faster it will travel upwards.Ê
air
When the blow on the gum, air builds up and comes out as a bubble.
by air
Air.
Sealed air
If you are asking about a bubble in a liquid, the answer is that the bubble has lower density (the gas inside is "lighter") than the surrounding liquid. If you are asking about a soap bubble, the answer is that air currents carry the bubble up. The bubble itself is not lighter than air (unless filled with another gas) but the film making the bubble is so thin and light that air currents can move it easily.
The air bubble could get lodged in the heart, preventing blood from flowing to the lungs.