Modelling shape-changing bubble in the water

Hi all,

I'd like to model a bubble changing shape in the water due to different pressure levels applied on the two domains. For now, I am running a test model with no applied pressure, but it kept telling "failure to find initial values", could someone please tell me where I did wrong?

Also, where do I set up the pressures in the water and the gas? I couldn't find it on the domain settings.

Many thanks!