Particles for underwater bubbles

 1. go to FX, click nParticles> Create Options> Balls

2. Creat a geometry under the model to emitting the particles

3.  select the geometry and go to nParticles>Emit from Object

4. adjust the nParticles values

 change the Gravity to -60, so the particle ball will floating up

5. Put the geometry into the model's bone group, so the geometry will follow her. Then just hide ( Ctrl+H) the geometry and only show the bubble.

6. If the particle didn't show, select the nParticles1 and go to Shading > Particle Render Type: Spheres

final look of bubble: