I ran the bubble simulation using pop solver. I start by selecting the mouth piece geometry from the diving gear, copying a bunch of spheres to points using the copy to points node. Then adding a trail node so that the bubbles trails along as the character moves and then painted where I wanted the bubbles (spheres) to populate from using a paint node. Using a few lines of code in VEX, I was able to make the bubbles size different. (When the spheres spawn in, they are in different sizes)

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The logic was there but it was broken (as for the first breakdown). The bubbles were going through the helmet even though it was set as a collider, and the bubbles were very round. It was a little bit confusing as I got the setup right. 

 

I was able to brainstorm this problem with a friend and found out why it the colliders were not working - it was because the helmet's visor was a plane and Houdini wasn't reading it as a 'collider mesh'. So I extruded it inwards and made the visor thick, and then merged the visor, helmet and the rest of the geometries together and put them as collider.

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(Second breakdown where the bubbles were red) I also turned the helmet into a VDB and then it worked perfectly fine! After it was clear that the bubbles are bouncing off the helmet, - for the bubbles to make it look blobby, I converted the spheres to VDB then back out as polygon and it splits and clumps together!