  We study the impact of the ambient fluid on the evolution of collapsing false
vacuum bubbles by simulating the dynamics of a coupled bubble-particle system.
A significant increase in the mass of the particles across the bubble wall
leads to a buildup of those particles inside the false vacuum bubble. We show
that the backreaction of the particles on the bubble slows or even reverses the
collapse. Consequently, if the particles in the true vacuum become heavier than
in the false vacuum, the particle-wall interactions always decrease the
compactness that the false vacuum bubbles can reach making their collapse to
black holes less likely.
