You and Estre casually float down to the vents and pretend to pull Arraia aside for some mundane chatter about some of the food here. It's not until you're safely away from the crowd that Estre brings up Cinza.
He links an arm around Arraia's and starts leading her back to the city. "I think we should visit an old friend, don't you?" he says. "Someone who couldn't attend this party."
Arraia looks at you anxiously. You clarify: "Someone who was stuck getting a little more air than she'd like."
Arraia's face brightens in understanding. "I'm in," she says.
You three swim toward the city, but once you reach the entrance, you swim up above it instead. Nobody follows you, and now there's nobody to interfere. You stop to hide behind a ballast pump far away enough from Cinza that the guards won't be able to notice you spying on them.
Estre turns to you. "Now that we're all here together, what's the plan?" he asks. "If we're going to get Cinza out, we have to get past the guards." You look over at the air ballast that's housing Cinza. She's still up in the giant crystal air bulb, sitting down on her legs, with nothing to do, nothing to read. Two guards are stationed at the entrance of the ballast's single, narrow stem.