Need help identifying this bubble?

[Mizu]

Hi everyone, I got a pair of Nassarius snails a few days ago and one of them went missing for about 36 hours. Just now I found both of them moving about, one of them climbed all the way to my waterline and I noticed these weird bubbles at my water line. It's one big bubble surrounded by smaller bubbles and my snail keeps going up the glass and eventually falling off only to keep climbing back up. These aren't eggs right?

 

[KrisReef]

Right

 

[AlyciaMarie]

They look like regular bubbles to me.

 

[Gumbies R Us]

I think they are just normal-looking bubbles.